Why is the ninth month called September?
Old English hærfest "autumn, period between August and November," from Proto-Germanic *harbitas (cf. Old Saxon hervist, Old Frisian and Dutch herfst, German Herbst "autumn," Old Norse haust "harvest"), from PIE *kerp- "to gather, pluck, harvest" (cf. Sanskrit krpana- "sword," krpani "shears;" Greek karpos "fruit," karpizomai "make harvest of;" Latin carpere "to cut, divide, pluck;" Lithuanian kerpu "cut;" Middle Irish cerbaim "cut").
The borrowing of autumn and the use of fall in a seasonal sense gradually focused the meaning of harvest to "the time of gathering crops" (mid-13c.), then to the action itself and the product of the action (after c.1300). Figurative use by 1530s. Harvest home (1590s) is the occasion of bringing home the last of the harvest; harvest moon (1706) is that which is full within a fortnight of the autumnal equinox.
c.1400, from harvest (n.). Of wild animals, from 1947; of cells, from 1946. Related: Harvested; harvesting.
the season for gathering grain or fruit. On the 16th day of Abib (or April) a handful of ripe ears of corn was offered as a first-fruit before the Lord, and immediately after this the harvest commenced (Lev. 23:9-14; 2 Sam. 21:9, 10; Ruth 2:23). It began with the feast of Passover and ended with Pentecost, thus lasting for seven weeks (Ex. 23:16). The harvest was a season of joy (Ps. 126:1-6; Isa. 9:3). This word is used figuratively Matt. 9:37; 13:30; Luke 10:2; John 4:35. (See AGRICULTURE.)