Montesquieu

“Marriages among the Germans are severe,” says Tacitus ; “vices are not a sub­ject of ridi­cule to them1 ; to cor­rupt or be cor­rup­ted are not consi­de­red a cus­tom or a man­ner of living ; "there are few exam­ples in such a popu­lous nation of the vio­la­tion of conju­gal troth.”2

That explains the expul­sion of Childeric : he affron­ted rigid ways which the conquest had not had time to change.

Severa matrimonia…..nemo illic vitia ridet, nec corrumpere et currumpi sæculum vocatur (De moribus Germanorum).

Paucissima in tam numerosa gente adulteria (ibid.).