Did the Greek term 'κεραία' (keraia) derive from the Ivri term 'Kera' ( כְרָעַ֨ )?
Greek keraía comes from Ancient kerás "horn", from Proto-Indo-European *ḱerh₂-, cognate with English "horn" (and also the second half of "unicorn", via Latin, and various others in other languages).
There's been some suggestion that this word could be related to Proto-Semitic *qarn-, ancestor of Hebrew qeren. But the exact details of this (such as who borrowed it from whom) are lost to time.
I'm not aware of any connection to keraʕ; the meanings seem totally unrelated ("horn" versus "kneel down"), so I wouldn't expect any sort of relation there.