1650s, "to confirm by circumstances," from Latin circumstantia "surrounding condition" (see circumstance) + -ate (2). It was used earlier in a now-obsolete sense "place in particular circumstances" (1630s). Related: Circumstantiated; circumstantiating; circumstantiation.

c. 1600, "attending, incidental," also "derived from circumstances," from Latin circumstantia (see circumstance) + -al (1). Related: Circumstantially. Legalese circumstantial evidence "evidence from more or less relevant circumstances bearing upon a case," as distinguished from direct testimony, is attested by 1691.

"by what, by which," c. 1200, from where (in the sense of "in which position or circumstances") + by.

"state of mind which results from satisfaction with present circumstances," 1570s, from content (adj.). Phrase heart's content is from 1590s (Shakespeare).

"at what, at which," mid-13c., from where (in the sense of "in which position or circumstances") + at.

"with which, that with which," c. 1200, from where (in the sense of "in which position or circumstances") + with.

"on which," c. 1200, from where (in the sense of "in which position or circumstances") + on (adv.).