hay

Etymology 1

From Middle English hey, from Old English hīeġ, from Proto-West Germanic *hawi, from Proto-Germanic *hawją (compare West Frisian hea, Dutch hooi, German Heu, Norwegian høy), from *hawwaną (“to hew, cut down”). More at hew.

noun

1. (uncountable) Grass cut and dried for use as animal fodder.
   Hay may be dried too much as well as too little. 1857, Charles Louis Flint, Grasses and Forage Plants: A Practical Treatise, […]
2. (countable) Any mix of green leafy plants used for fodder.
3. (slang) Cannabis; marijuana.
   I would like some of that hay. Enclose $20. 1947, William Burroughs, letter, 19 Feb 1947
   Jeff Spicoli, roll me another hay 1994, “Bug Powder Dust”, performed by Bomb the Bass
4. A net set around the haunt of an animal, especially a rabbit.

verb

1. To cut grasses or herb plants for use as animal fodder.
2. To lay snares for rabbits.

Etymology 2

From Middle English haye, heye, a conflation of Old English heġe (“hedge, fence”) and Old English ġehæġ (“an enclosed piece of land”).

noun

1. (obsolete) A hedge.
2. (obsolete) A net placed around the lair or burrow of an animal.
3. (obsolete) An enclosure, haw.
4. (obsolete) A circular country dance.

Etymology 3

From the sound it represents, by analogy with other letters such as kay and gay. The expected form in English if the h had survived in the Latin name of the letter "h", hā.

noun

1. The letter for the h sound in Pitman shorthand.