off-season (n.)

by c. 1200 as an emphatic form of Old English of (see of), employed in the adverbial use of that word. The prepositional meaning "away from" and the adjectival sense of "farther" were not firmly fixed in this variant until 17c., but once they were they left the original of with the transferred and weakened senses of the word. Meaning "not working" is from 1861.

Off the cuff "extemporaneously, without preparation" (1938) is from the notion of speaking from notes written in haste on one's shirt cuffs. In reference to clothing, off the rack (adj.) "not tailored, not made to individual requirements, ready-made" is by 1963, on the notion of buying it from the rack of a clothing store; off the record "not to be publicly disclosed" is from 1933; off the wall "crazy" is 1968, probably from the notion of a lunatic "bouncing off the walls" or else in reference to carom shots in squash, handball, etc.

c. 1300, sesoun, seson, "a period of the year," with reference to weather or work, also "proper time, suitable occasion," from Old French seison, seson, saison "season, date; right moment, appropriate time" (Modern French saison) "a sowing, planting," from Latin sationem (nominative satio) "a sowing, planting," noun of action from past-participle stem of serere "to sow" (from PIE root *sē- "to sow").

The sense shifted in Vulgar Latin from "act of sowing" to "time of sowing," especially "spring," regarded as the chief sowing season. In Old Provençal and Old French (and thus in English), this was extended to "any one of the four natural periods of the year," especially as determined astronomically by solstices and equinoxes. Later it was extended to the recurring annual wet and dry periods of the Tropics (1719).

In other Indo-European languages, generic "season" (of the year) words typically are from words for "time," sometimes with a word for "year" (as in Latin tempus (anni), German Jahreszeit). Spanish estacion, Italian stagione are unrelated, being from Latin statio "station."  

The season, short for some particular annual festivity, is by 1791 (hence season's greetings, etc.). Sometimes merely meaning "period of time," as in for a season. Man for all seasons, one for all times and circumstances, is from 1510s.

The meaning "time of year when an animal is hunted or killed for food" (as in in season) is from late 14c. The sense of "period of time regularly devoted to a particular sport or amusement" is by 1680s. Meaning "time of year during which a place is most frequented" is from 1705. Season ticket, one giving the holder unlimited use, admission, etc. for a specified period, is attested from 1820.