"matter used in vaccination," 1846, from French vaccin, noun use of adjective, from Latin vaccina, fem. of vaccinus "pertaining to a cow" (see vaccination). Related: Vaccinal; vaccinic.

1590s, "to sway unsteadily," from Latin vacillatus, past participle of vacillare "sway to and fro; hesitate" (see vacillation). Meaning "to waver between two opinions or courses" is recorded from 1620s. Related: Vacillated; vacillates; vacillating.

c. 1400, "hesitation, uncertainty," from Latin vacillationem (nominative vacillatio) "a reeling, wavering," noun of action from past-participle stem of vacillare "sway to and fro, waver, hesitate, be untrustworthy," of uncertain origin. Originally in reference to opinion or conduct; literal sense is recorded from 1630s.

late 14c., "hollow space," from Latin vacuitas "empty space, emptiness, absence, vacancy, freedom," from vacuus "empty," from PIE *wak-, extended form of root *eue- "to leave, abandon, give out." Originally in anatomy. Meaning "vacancy of mind or thought" is attested from 1590s.

"small cavity or vesicle," 1853, from French vacuole, from Medieval Latin vacuola, formed as a diminutive of Latin vacuus "empty," from PIE *wak-, extended form of root *eue- "to leave, abandon, give out."

1640s, "empty" (implied in vacuousness), from Latin vacuus "empty, void, free" (from PIE *wak-, extended form of root *eue- "to leave, abandon, give out"). Figurative sense of "empty of ideas, without intelligent expression" is from 1848. Related: Vacuously.

"to clean with a vacuum cleaner," by 1913, from vacuum (n.). Related: Vacuumed; vacuuming.

1540s, "emptiness of space," from Latin vacuum "an empty space, vacant place, a void," noun use of neuter of vacuus "empty, unoccupied, devoid of," figuratively "free, unoccupied," from Proto-Italic *wakowos, related to the source of Latin  vacare "to be empty" (from PIE *wak-, extended form of root *eue- "to leave, abandon, give out"), with adjectival suffix -uus. Properly a loan-translation of Greek kenon, literally "that which is empty."

Meaning "a space emptied of air" is attested from 1650s. Vacuum tube "glass thermionic device" is attested from 1859. Vacuum cleaner is from 1903; shortened form vacuum (n.) first recorded 1910.

The metaphysicians of Elea, Parmenides and Melissus, started the notion that a vacuum was impossible, and this became a favorite doctrine with Aristotle. All the scholastics upheld the maxim that "nature abhors a vacuum." [Century Dictionary]

Latin, imperative singular of vadere "to go" (see vamoose).

"a pocket manual, handbook," 1620s, Latin, literally "go with me;" from imperative of vadere "to go" (see vamoose) + me "me" + cum "with."