"flat, square table or slab under the molding of the base of a Roman column; square molding at the base of any architectural part," 1610s, from French plinthe (16c.) and directly from Latin plinthus, from Greek plinthos "brick, squared stone," from PIE *splind- "to split, cleave," from root *(s)plei- "to splice, split" (see flint).
1560s, from Italian squadrone, augmentative of squadra "battalion," literally "square" (see squad). As a division of a fleet, from 1580s, of an air force, 1912.
square cap worn by Catholic clergy, 1590s, from Italian beretta, from Late Latin birrus, birrum "large cloak with hood;" which is perhaps of Gaulish origin, or from Greek pyrros "flame-colored, yellow."
also do-se-do, common step in square-, contra-, polka-dancing, etc., 1929, from French dos-à-dos "back to back" (see dossier).
1560s, "a leisurely walk, a walk for pleasure or display," from French promenade "a walking, a public walk" (16c.), from se promener "go for a walk," from Late Latin prominare "to drive (animals) onward," from pro "forth" (see pro-) + minare "to drive (animals) with shouts," from minari "to threaten" (see menace (n.)).
Meaning "place for walking" is from 1640s; specifically "walkway by the sea" (from late 18c.); British sense of "music hall favored by 'loose women and the simpletons who run after them' " [The Observer, Jan. 18, 1863, in reference to the Alhambra in Leicester Square] is attested from 1863. Sense of "a dance given by or at a school" is from 1887.
name of the letter M, c. 1200, from Latin; the Greek name was mu. In printing, originally the square corresponding in dimensions to the capital M of that type.