gubernaculum

noun

gu·​ber·​nac·​u·​lum ˌgü-bər-ˈnak-yə-ləm 

plural gubernacula -lə 

: a part or structure that serves as a guide

especially : a fibrous cord that connects the fetal testis with the bottom of the scrotum and by failing to elongate in proportion to the rest of the fetus causes the descent of the testis