suit (n.)

c. 1300, sute, also suete, suite, seute, "a band of followers; a retinue, company;" also "set of matching garments" worn by such persons, "matching livery or uniform;" hence "kind, sort; the same kind, a match;" also "pursuit, chase," and in law, "obligation (of a tenant) to attend court; attendance at court."

This is from Anglo-French suit, siwete, from Old French suite, sieute "pursuit, act of following, hunt; retinue; assembly" (12c., Modern French suite), from Vulgar Latin *sequita, fem. of *sequitus, from Latin secutus, past participle of sequi "to attend, follow" (from PIE root *sekw- (1) "to follow").

The legal sense of "lawsuit; legal action, proceeding in a court of justice" is from mid-14c. The meaning "the wooing of a woman" is from late 15c.

By late 14c. in reference to any matched set of objects; the meaning "row, series, sequence" also is attested from late 14c., as is the sense of "set of clothes to be worn together; hence its use as a derisive term for "businessman" (1979).

It is also attested from late 14c. as "matching material or fabric," from the notion of the livery or uniform of court attendants. The meaning "class of playing cards bearing the same symbol" is attested from 1520s, also ultimately from the notion of livery. To follow suit (1670s) is from card-playing: "play a card of the same suit first played," hence, figuratively, "continue the conduct of a predecessor."

mid-14c., suten, "be becoming;" 1570s, "be agreeable or convenient, fall in with the views of," from suit (n.), perhaps on the notion of "join a retinue clad in like clothes."

Earlier it meant "seek out" (mid-15c.), and formerly also had many of the senses of sue (v.).

The meaning "make agreeable or convenient" is from 1590s. The sense of "be fitted or adapted to, answer to the requirements of" is from c. 1600.

The transitive meaning "provide (someone) with clothes" is from 1570s; that of "dress oneself" is from 1590s; with up (adv.) from 1945, American English. Expression suit yourself "do as you please" is attested by 1851. Related: Suited; suiting.