1. from what place, source, or cause
The Collaborative International Dictionary of English v.0.48:
Whence \Whence\, adv. [OE. whennes, whens (with adverbial s,
properly a genitive ending; -- see -wards), also whenne,
whanene, AS. hwanan, hwanon, hwonan, hwanone; akin to D.
when. See When, and cf. Hence, Thence.]
1. From what place; hence, from what or which source, origin,
antecedent, premise, or the like; how; -- used
Whence hath this man this wisdom? --Matt. xiii.
Whence and what art thou? --Milton.
2. From what or which place, source, material, cause, etc.;
the place, source, etc., from which; -- used relatively.
Grateful to acknowledge whence his good
Note: All the words of this class, whence, where, whither,
whereabouts, etc., are occasionally used as pronouns by
a harsh construction.
O, how unlike the place from whence they fell?
Note: From whence, though a pleonasm, is fully authorized by
the use of good writers.
From whence come wars and fightings among you?
--James iv. 1.
[1913 Webster] Of whence, also a pleonasm, has become
WordNet (r) 3.0 (2006):
adv 1: from what place, source, or cause
Moby Thesaurus II by Grady Ward, 1.0:
42 Moby Thesaurus words for "whence":
accordingly, away, because of that, because of this, consequently,
derivation, ergo, for that, for that cause, for that reason,
for this cause, for this reason, for which reason, forth, fountain,
hence, hereat, inception, off, on that account, on that ground,
on this account, origin, out, propter hoc, provenance, provenience,
root, then, thence, thereat, therefor, therefore, therefrom,
thereof, thus, thusly, thuswise, well, wellspring, wherefore,