"base frame of an automobile," 1903, American English; earlier "sliding frame or carriage-base for a large gun" (1869), "window frame" (1660s), from French châssis "frame," Old French chassiz (13c.) "frame, framework, setting," from chasse "case, box, eye socket, snail's shell, setting (of a jewel)," from Latin capsa "box, case" (see case (n.2)) + French -is, collective suffix for a number of parts taken together. Compare sash (n.2).
1640s, "a musical performance at night in open air" (especially "one given by a lover under the window of his lady" [OED]), from French sérénade (16c.), from Italian serenata "an evening song," literally "calm sky," from sereno "the open air," noun use of sereno "clear, calm," from Latin serenus "peaceful, calm, serene" (see serene (adj.)). The sense was influenced by Italian sera "evening" (from Latin sera, fem. of serus "late"). The meaning "piece of instrumental music suitable for a serenade" is attested from 1728.
1630s, "type of plasterer's fine paste or cement," from French potée "polishing powder" (12c.), originally "pot-full, contents of a pot," from Old French pot "container" (see pot (n.1)).
From 1660s as "powder used for polishing glass or metals." The meaning "soft pasty mixture for sealing window panes" is recorded by 1706. Figurative use in reference to one easily influenced is from 1924. Putty knife, one with a blunt, flexible blade, used by glaziers, etc., for laying on putty, is attested from 1834.