A
Name: Ailm - pine tree(?) [wailing]
Pronunciation: AE-lum
Color: alad - piebald [spotted, usually black and white]
Tree: fir, pine(?)
Bird: aidhircleóg - lapwing
MM: ardam íachta: loudest of groanings, loudest of groans
MO: tosach frecrai: beginning of an answer
CC: tosach garmae: beginning of expressions, beginning of calling
Deities: Macha the Mother of Twins, Danu as Great Mother
Meanings: birth and death, pregnancy, child(ren), cycle of life, origination, inception, conception, creation, initial understanding, an "ah-ha" experience
Notes: The word ailm is attested only once in the literature, and appears to mean "pine tree," but this is entirely conjectural. I assigned "wailing" to this letter based on the word ogams, which point to the groans of birth and death pangs, and to the "ah" of understanding when one begins to apprehend or express an answer to a deep question. In the Amra Choluim Chille, the letter a is glossed with "between his two a's, i.e. the a of his birth and the a of his death," regarding the "ah" cry of the newborn and the dying.

O
Name: Onn - ash tree; wheel, turning, movement, sole of the foot, foundation
Pronunciation: on
Welsh: onen - ash tree, possibly cognate with L: ornus - mountain ash or rowan
Root: IE: *os-, *osen-, ash-tree; OI: onn, ash tree (though it is more often uinniuis or uinnsiu by the period when the Book of Ballymote was written); OI: (f)onnaid, turning, swift movement, wheel of a chariot, wanderer
Color: odhar - dun
Tree: furze, ash, whin, heather
Bird: odoroscrach - scrat
MM: congnaid ech: helper of horses i.e. the wheels of a chariot, wounder of horses; hastener of horses (horsewhip)
MO: féthem soíre: smoothest of work; smoothest of craftsmanship
CC: lúth fían; desire of the fianna i.e. heather, sustaining equipment of warrior or hunting bands
Deities: Manannán as Gatekeeper and Lord of Mists, Láeg the Charioteer of Cú Chulainn, Maíle Dúin
Meanings: travel, journeys, movement in a static situation, spiritual journey work, working within the Otherworlds, guidance, guiding spirits, building foundations
Notes: Two word ogams here point to the meaning of wheel or movement, as does the OI fonnaid. The idea of the horsewhip suggests furze, while the sustaining equipment of a warrior or hunter would suggest spears, made from ash wood.
   My preference is for the wheel, turning, movement meaning set based on fonn, sole of the foot (and foundation) -- which implies walking or journeying -- or (f)onnaid suggested by Meroney. McManus doesn't even suggest this for a possible interpretation, preferring the "ash" reading.
   Fonnaid has four distinct meanings: the wheel of a chariot, swift movement, a wanderer, and turning, movement or removal. The Duil Feda ("Elements of Letters") section in the Book of Ballymote uses the word "onnaid" to indicate the wheels of a chariot, and is a variant spelling of fonnaid. All of these meanings for fonnaid lead me to the idea of movement and journeys, and the other meanings expand from that basis.

U
Name: Úr - humus, earth, soil, clay; Úir - grave, burial, flesh
Pronunciation: oor
Color: usghda - resinous [amber]
Tree: thorn, heather
Bird: uiseóg - lark
MM: úaraib adbaib: in cold dwellings
MO: sílad cland: propagation of plants, seeding up of plants
CC: forbbaíd ambí: shroud of a lifeless one, shroud of the lifeless i.e. soil
Additional word ogams exist for this fid: gruidem dál: most prompt of meetings, guiremh dál: nearest of meetings - metaphors for "death, grave, earth" according to Meroney.
Deities: Anu or Danu as the land mother whose breasts are mountains
Meanings: death, graves and graveyards, ghosts, hauntings, memories of the dead, burial, grieving, the cycle of life and death, the end of a cycle, something inescapable, the body, physicality, embodiment of a spiritual principle, land, the earth or biosphere, land spirits, wild plants, caves or caverns
Notes: The word ogams and word meanings are fairly clear in leading to the various divinatory meanings I've chosen. Meroney's elaborate glossing simply gives extra weight to the death/grave aspects of the fid. As with the death card in the Tarot, death can as easily be a metaphor as an actual death or end of a cycle. Clay is a common metaphor for flesh or the body, particularly in the context of death and the grave.

E
Name: Edad - [fly agaric or amanita muscaria]
Pronunciation: ED-uhth
Color: erc - red-speckled
Tree: yew, aspen
Bird: ela - swan
MM: érgnaid fid: discerning tree, distinguished wood
MO: commaín carat: exchange of friends, synonym for a friend
CC: brátahir beithi: brother of birch
There are additional word ogams for this fid: aercaid fer no fid: plant or tree of harm; erchra fer; plant of destruction. Commaín carat is glossed in one place as clesach uisce "tricky in water," i.e. éiccne "a variety of salmon," but this would seem more rightly to match with the forfeda fid Ea (ebad), which has a very direct link to a meaning of salmon through its word ogams.
Deities: Oengus mac ind Og as bringer of dreams
Meanings: divination, dreams, visions, seeking of dreams and visions, intoxication, discernment, enlightenment, tools used to achieve visions or ecstasy, connection with the Otherworlds, communication with the sídhe and Otherworld beings
Notes: Edad, as Idad below, are not actual words in any form of Irish. Neither Meroney nor McManus were able to discover any relevant root words to point at a meaning. This means that we have to depend on the word ogams and our own intuitions to derive meanings for these letters.
   I chose to emphasize the word ogam "brother of birch" and to interpret that as the amanita muscaria mushroom. In my mind, this is aided by the color ogam of "red-speckled," which is how one could describe the red-capped, white-speckled mushroom Additionally, the "plant of destruction" or "plant of harm" word ogams would point to the popular belief that the amanita muscaria is poisonous, when in fact it is a commonly used visionary mushroom in much of the world where it occurs. More discussion of the amanita muscaria and its possible links to Filidecht can be found in the 1997 article I wrote with Timothy White for Shaman's Drum.    If the forfeda are not being used, "salmon" can be an alternate reading for this fid.

I
Name: Idad - yew (?) [age]
Pronunciation: IH-duth
Color: irfind - very white
Tree: yew (?), service tree, ivy (?)
Bird: illait - eagle
MM: sinem fedo: oldest of woods, oldest tree, oldest letter, older than letters
MO: caínem sen: fairest of the ancients
CC: lúth lobair: energy of an infirm person
Other word ogams exist for this fid: crinam feada no cláinem: most withered of wood, crookedest of wood; cáined sen no aileam áis: lovely wood, most pleasant of growth. Also on this fid is the gloss of claidem: sword.
Deities: Caílte and Oisín as the ancient survivors of the Fianna, Tuan mac Cairell
Meanings: history, the past, ancient memory, old stories, lore, tradition, immortality, reincarnation, past lives, age and aging, elders, endurance, permanence
Notes: As with the previous fid, this has no obvious meaning or root for its name, though the word ogams do suggest the yew, which appears to be the longest-lived tree in the world. From this implication of great age, I derive the other meanings suggested here.