This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
喗 combines 口 (mouth) with 軍, which likely provides the sound. The exact historical development is uncertain.
With 口 (mouth) beside 軍 (army), picture a soldier's mouth giving a command, but the true meaning is uncertain.
For ギン, imagine a soldier in the 軍 army giving a command with a grin: grin -> ギン.
—