Where does “Graeco-Bactrian” come from?

Graeco-Bactrian (English) comes from English Graeco-, from Latin Graecus, from Ancient Greek Γραικός, from Ancient Greek γραῖα, from Proto-Indo-European ǵerh₂- — to grow old, to mature.

Ancestry of “Graeco-Bactrian”, step by step

Step	Language	Word	Meaning
1	English	Graeco-	Greece; Greek
2	Latin	Graecus	Greek, Grecian, of or pertaining to the Greek...
3	Ancient Greek	Γραικός	Greek; a Graecian, a member of an ancient...
4	Ancient Greek	γραῖα	Graea, Boeotia; Greece
5	Proto-Indo-European	ǵerh₂-	to grow old, to mature

Every word from Proto-Indo-European ǵerh₂- →Every word from Ancient Greek γραῖα →Every word from Ancient Greek Γραικός →