Leftenant

I always wonder why Brits say "leftenant" for "lieutenant", and found some information that explains why:

In the time of Chaucer (1340?-1400), the distinction between the letters u and v did not yet exist in writing. Once they separated, people remained uncertain as to which sound each of these letters represented. Another theory focuses on auditory rather than visual confusion.

Read the rest of the explanation to find out a lot more.