'syngamic' originates from Greek, specifically the element 'syn-' (from Greek σύν) meaning 'together' and 'gamos' (γάμος) meaning 'marriage' or 'union', via New Latin/Modern scientific usage of 'syngamy'.

'syngamic' developed from New Latin/Medieval Latin terms such as 'syngamia' (referring to union or marriage), passed into scientific Latin as 'syngamy' for gamete fusion, and then formed into the English adjective 'syngamic'.

Initially it referred broadly to 'marriage' or 'union' (literal or social), but in biological and scientific usage it evolved to mean specifically the 'fusion of gametes' and things relating to that process.