late 14c. (from c. 1100 as a surname), "a worker in any sort of lead" (roofs, gutters, pipes), from Old French plomier "lead-smelter" (Modern French plombier) and directly from Latin plumbarius "worker in lead," noun use of adjective meaning "pertaining to lead," from plumbum "lead" (see plumb (n.)). The meaning focused 19c. on "workman who installs pipes and fittings" as lead pipes for conveying water and gas became the principal concern of the trade.
In U.S. history, in the Nixon administration (1969-74), it was the name of a special unit for investigation of "leaks" of government secrets.
Meaning "action of inflating with air or gas" is from c. 1600. Monetary sense of "enlargement of prices" (originally by an increase in the amount of money in circulation) first recorded 1838 in American English.