How did the saying "catch as catch can" originate and what does it really mean?

The Oxford English Dictionary lists “catch as catch can” and “catch that catch may” as “phrases expressing laying hold of in any way, each as he can.”

There are examples going back to Chaucer and Gower in the 14th century. Many early phrases have “who” or “that” rather than “as”; so the sense seems to have been “let anyone who can catch do so”, i.e. “everyone for himself” or “grab what you can”.

From the seventeenth century onwards the phrase also described a style of wrestling: this sense seems to have been picked up by the French, who still call all-in wrestling “le catch”.