"the male organ of copulation," 1670s, from French pénis or directly from Latin pēnis "penis," earlier "tail," from PIE *pes-, usually said to be originally "penis" (source also of Sanskrit pasas-, Greek peos, posthe "penis," probably also Old English fæsl "progeny, offspring," Old Norse fösull, German Fasel "young of animals, brood"). But de Vaan writes that "the meaning of pēnītus ['furnished with a tail'] as well as general semantic considerations suggest that the meaning 'tail' is original, and 'penis' metaphorically derived from it." The proper plural is penes. The adjective is penial. In psychological writing, the term penis envy is attested by 1922.

jocular or slighting term for a clerk or author, by 1820, from pen (n.1) + driver. Earlier was quill-driver (by 1760).

The Author goes on, and tells us, "that the two thousand hogs were not driven into the sea by evil spirits, but by the two madmen, who, in one of their frantic fits, frightened them into it."— But is it not more than intimated that the men were restored to their right mind before the hogs took to their heels? Besides, that two madmen should drive two thousand such ungovernable creatures as hogs one way, does, I think, exceed the belief of any hog-driver on the road, if not of the pen-driver in his closet. [introduction to "Beelzebub Driving and Drowning his Hogs," a sermon on Mark v.12, 13, by James Burgess, 1820]

heavy metal, Old English lead "lead, leaden vessel," from West Germanic *lauda- (source also of Old Frisian lad, Middle Dutch loot, Dutch lood "lead," German Lot "weight, plummet"), a word of uncertain origin. The name and the skill in using the metal seem to have been borrowed from the Celts (compare Old Irish luaide).

Figurative of heaviness at least since early 14c. American English slang lead balloon "dismal failure" attested by 1957, perhaps 1940s (as a type of something heavy that can be kept up only with effort, from 1904). Lead-footed "slow" is from 1896; opposite sense of "fast" emerged 1940s in trucker's jargon, from notion of a foot heavy on the gas pedal.

Meaning "graphite in a pencil" is from 1816 (see pencil (n.)). Black lead was an old name for "graphite," hence lead pencil (1680s) and the colloquial figurative phrase to have lead in one's pencil "be possessed of (especially male sexual) vigor," attested by 1902. White lead (1560s) was an old name for "tin."

As a name of a dull bluish-gray color, 1610s. From 1590s as figurative for "bullets." Lead oxide was much used in glazing, mirror-making, and pigments. In printing, "thin strip of type-metal (often lead but sometimes brass) used in composition to separate lines" from 1808, earlier space-line. Lead-poisoning is from 1848; earlier lead-distemper (1774).

antibiotic agent active against bacteria but harmless to most persons, 1929, coined in English by Alexander Fleming (1881-1955), who first recognized its antibiotic properties, from Modern Latin Penicillium notatum (1867), the name of the mould from which it was first obtained, from Latin penicillus "paintbrush" (see pencil (n.)), in reference to the shape of the mould cells.