Oh I didn't know this one. For me the mnemonic was " 'ba' has an 'a' like 'gauche' (left), and 'tri' has an 'i' like 'droite' (right)".

In Spanish, it's babor and estribor. My personal mnemonic (me and most people being right-handed) is that the estribo (the stirrup, but I always though it was the reins - TIL) in a horse go on the right hand and the boba hand (the clumsy hand) is the left one.

In German it is Steuerbord und Backbord. And my mnemonic is the "r" in Steuerbord = the "r" in right hand side (when looking to the bow that is).

Both likely come from (middle) dutch bakboord (the side of your back) facing the stierboord (the side with the steering oar) . Stierboord became estribord then tribord. Its more explicit in modern german and dutch.