tilde (n.)

c. 1300, "inscription, heading" on or over an object, originally especially the superscription on Christ's Cross, from Old French title "title or chapter of a book; position; legal permit" (12c., Modern French titre, by dissimilation), and in part from or merged with Old English titul. Both are from Latin titulus "inscription, label, ticket, placard, heading; honorable appellation, title of honor," a word of unknown origin.

The notion is an inscription placed over something to distinguish or specialize it. The meaning "name of a book, poem, play, etc." is recorded by late 14c. The sense of "subdivision heading in a book" (14c.) is preserved in law books and legal documents. In the publishing trade, "any book, magazine, or newspaper," by 1895.

It is attested by early 14c. as "a deed giving legal right to possession of land or property;" hence the right of ownership itself. The legal sense of "claim, reason, or cause; justification for an act" is late 14c.

The sense of "name showing the rank of a person or family," hence more generally "distinguishing appellation" belonging to someone by right or endowment or as a mark of respect, is attested from 1580s.

The sports championship sense is attested from 1913 (in lawn tennis), hence titlist (1913). Title-holder is by 1904 in a legal sense, by 1938 in sports. The title-page (1610s) is the preliminary page in a book or other printed publication. A title role in theater (1886) is one which gives its name to the play. Also compare tittle (n.). Title-insurance (1902) protects real-estate holders against defective titles.

"small stroke or mark made by a pen-point in writing," late 14c., titil (Wycliffe, in Matthew v.18); it is title (n.) with a specialized sense (which developed in Late Latin and Romanic) and pronunciation. In Wycliffe it translates Latin apex in the Late Latin sense of "accent mark over a vowel," which itself translates Greek keraia (literally "a little horn"), used by the Greek grammarians of the accents and diacritical points. In this case the Greek word is a Biblical translation of Hebrew qots, literally "thorn, prick," used of the little lines and projections by which the Hebrew letters of similar form differ from one another.

Wycliffe's word is borrowed from a specialized sense of Latin titulus, which was used in Medieval Latin (and in Middle English and Old French) to indicate "a stroke over an abridged word to indicate letters missing" (compare Provençal titule "the dot over -i-", and tilde, which represents in English the Spanish form of the same word; also see iota).

As apex was used by the Latin grammarians for the accent or mark over a long vowel, titulus and apex became to some extent synonymous; hence Wyclif's use of titil, titel to render L. apex [OED]

As "smallest or very small part of something" by late 14c. (compare jot (n.)). The phrase to a tittle "with great exactness" is from c. 1600.