Origin of octa-
Examples from the Web for octa
The incautious sovereign having assented to this, Octa and Ebusa arrived with forty ships.
After this Eosa and the rest that fled, being encouraged by Octa's success, came also, and were admitted to the same favour.
before vowels oct-, word-forming element meaning "eight," from Greek okta-, okt-, from PIE *okto(u) "eight" (see eight). The variant form octo- often appears in words taken from Latin, but the Greek form is said to be the more common in English.