"Mono a mono" and other delights

Apropos of nothing at all, here's a long list of usage errors I came across while researching what is probably the most distinctive mistake from amateur fantasy games and writing. Here, the second most distinctive. Some of these solecisms have a certain wit: "old-timer's disease," "trite and true," "soup du jour of the day." Others are all too familiar from people trying to write Olde English or confusing Greek, English and Spanish. And one that is near and dear to my heart.

That's "Olde", not Old, Beowulf.

Speaking of Olde English, here is how to use terms like "thee" and "thou" correctly.

Any other recurrent mistakes in genre writing I missed?