"be agreeable or convenient, fall in with the views of," 1570s, from suit (n.), perhaps from the notion of "join a retinue clad in like clothes." Earlier "seek out" (mid-15c.); "be becoming" (mid-14c.). Meaning "make agreeable or convenient" is from 1590s. Meaning "provide with clothes" is from 1570s; that of "dress oneself" is from 1590s; with up (adv.) from 1945. Expression suit yourself attested by 1851. Related: Suited; suiting.
Old English fyllan "to fill, make full, fill up, replenish, satisfy; complete, fulfill," from Proto-Germanic *fulljanan "to fill" (source also of Old Saxon fulljan, Old Norse fylla, Old Frisian fella, Dutch vullen, German füllen, Gothic fulljan "to fill, make full"), a derivative of adjective *fullaz "full" (see full (adj.)). Related: Filled.
To fill the bill (1882) originally was U.S. theatrical slang, in reference to a star of such magnitude his or her name would be the only one on a show's poster. To fill out "write in required matter" is recorded from 1880.
"brought to a full or completed state," 1746, past-participle adjective from round (v.).
1550s, "perfect, faultless;" c. 1600, "abundantly full," also "full of life or spirit," also "plentifully supplied" (with money, etc.), perhaps from flush (v.1) through the notion of a river running full, hence level with its banks. Meaning "even, level" is from 1620s, originally of ship's decks. In general use by 1791; in typography, 1900; in pugilism, 1812.