The Collaborative International Dictionary of English v.0.48:

Tilde \Til"de\, n. [Sp., fr. L. titulus a superscription, title,
   token, sign. See Title, n.]
   The accentual mark placed over n, and sometimes over l, in
   Spanish words [thus, [~n], [~l]], indicating that, in
   pronunciation, the sound of the following vowel is to be
   preceded by that of the initial, or consonantal, y.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tilde
    n 1: a diacritical mark (~) placed over the letter n in Spanish
         to indicate a palatal nasal sound or over a vowel in
         Portuguese to indicate nasalization

The Free On-line Dictionary of Computing (30 December 2018):

tilde

    "~" ASCII character 126.

   Common names are: ITU-T: tilde; squiggle; twiddle; not.
   Rare: approx; wiggle; swung dash; enyay; INTERCAL: sqiggle
   (sic).

   Used as C's prefix bitwise negation operator; and in
   Unix csh, GNU Emacs, and elsewhere, to stand for the
   current user's home directory, or, when prefixed to a login
   name, for the given user's home directory.

   The "swung dash" or "approximation" sign is not quite the same
   as tilde in typeset material but the ASCII tilde serves for
   both (compare angle brackets).

   [Has anyone else heard this called "tidal" (as in wave)?]

   (1996-10-18)