According to Mr. Chan, '⍼' first appeared in the character set that the STIX fonts business proposed (PDF file) in March 2000. In this proposal, '⍼' is described as 'RIGHT ANGLE WITH DOWNWARDS ...

A target date of September 2005 has been set for the release of STIX Fonts, a free set of special mainly mathematical characters that are used in scientific, technical, and medical publishing. The ...