The -ard/art suffix had already become a pejorative by that time (due to the association of “too much X, and therefore to negative excess”), so a bastard was a “(bad) (child) of the bast”, meaning “saddle”. That is, a child conceived in a makeshift bed, usually on the road, instead of properly in a marriage bed. Source
I’ve read that the -ard suffice meant ‘too much’. Wizard = too much wisdom, drunkard = drank too much. I wonder what ‘bastard’ meant too much of.
The -ard/art suffix had already become a pejorative by that time (due to the association of “too much X, and therefore to negative excess”), so a bastard was a “(bad) (child) of the bast”, meaning “saddle”. That is, a child conceived in a makeshift bed, usually on the road, instead of properly in a marriage bed. Source
Another one on illegitimate children: “Son of a gun” is a shortened “son of a gun deck”, i.e. conceived by a sailor on a gun deck.