It is the "-lein" in "Fräulein", but "-lein" isn't only for feminine nouns: the word "Männlein" also exists. I suspect "-erl" is the same, though I don't speak

It is the "-lein" in "Fräulein", but "-lein" isn't only for feminine nouns: the word "Männlein" also exists. I suspect "-erl" is the same, though I don't speak a dialect where it's used; some dialects have "-l" or "-li" which can also attach to any gender of noun (as in "Hansl" and "Gretl")