Article snapshot taken from[REDACTED] with creative commons attribution-sharealike license.
Give it a read and then ask your questions in the chat.
We can research this topic together.
Uchi Mata Gaeshi (内股返) is one of the techniques adopted later by the Kodokan into their Shinmeisho No Waza (newly accepted techniques) list. It is categorized as a foot technique, Ashi-waza.