This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
骹 combines 骨 (bone) with 交, which likely contributes a phonetic element. The exact historical development is uncertain.
The left side 骨 means bone, and the right side 交 suggests crossing or mixing. Imagine bones crossing or interlocking at a joint, but remember the meaning is uncertain.
For コウ, picture a bone doctor named Kou examining the crossed bones: Kou -> コウ.