Etymology
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sign (n.)

early 13c., "gesture or motion of the hand," especially one meant to communicate something, from Old French signe "sign, mark," from Latin signum "identifying mark, token, indication, symbol; proof; military standard, ensign; a signal, an omen; sign in the heavens, constellation."

According to Watkins, literally "standard that one follows," from PIE *sekw-no-, from root *sekw- (1) "to follow." But de Vaan has it from PIE *sekh-no- "cut," from PIE root *sek- "to cut" He writes: "The etymological appurtenance to seco 'to cut' implies a semantic shift of *sek-no- 'what is cut out', 'carved out' > 'sign'." But he also also compares Hebrew sakkin, Aramaic sakkin "slaughtering-knife," and mentions a theory that "both words are probably borrowed from an unknown third source."

It has ousted native token. Meaning "a mark or device having some special importance" is recorded from late 13c.; that of "a miracle" is from c. 1300. Zodiacal sense in English is from mid-14c. Sense of "characteristic device attached to the front of an inn, shop, etc., to distinguish it from others" is first recorded mid-15c. Meaning "token or signal of some condition" (late 13c.) is behind sign of the times (1520s). In some uses, the word probably is a shortening of ensign. Sign language is recorded from 1847; earlier hand-language (1670s).

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sign (v.)
c. 1300, "to make the sign of the cross," from Old French signier "to make a sign (to someone); to mark," from Latin signare "to set a mark upon, mark out, designate; mark with a stamp; distinguish, adorn;" figuratively "to point out, signify, indicate," from signum "identifying mark, sign" (see sign (n.)). Sense of "to mark, stamp" is attested from mid-14c.; that of "to affix one's name" is from late 15c. Meaning "to communicate by hand signs" is recorded from 1700. Related: Signed; signing.
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sign-up (n.)
"number who have signed up," 1926, from the verbal phrase; see sign (v.) + up (adv.).
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sign-in (n.)
1968, from the verbal phrase; see sign (v.) + in (adv.).
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re-sign (v.)

"sign again," 1805, from re- "back, again" + sign (v.). With hyphenated spelling and full pronunciation of the prefix to distinguish it from resign. Related: Re-signed; re-signing.

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signboard (n.)
also sign-board, 1630s, from sign (n.) + board (n.1).
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signer (n.)
1610s, agent noun from sign (v.). In American history, with reference to the Declaration of Independence, by 1865.
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signage (n.)
1972, in reference to signs on roads or outside stores, from sign (n.) + -age. Earlier in legal language with reference to affixing signatures.
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undersign (v.)
1570s, from under + sign (v.). Related: Undersigned; undersigning.
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