nouns - Why is a woman a "widow" and a man a "widower"?

There are lots of words that have male and female forms, and usually there are alternate suffixes to the words which indicate the gender; for example, "waiter" vs. "waitress", "mister" vs. "mistress", etc. The one that has always puzzled me, though, is "widow" and "widower". Following the form of the previous examples, I understand "widower" for men--but why the form of the word with no suffix for women? Why isn't a woman called a "widowess"?

Answer

I suspect because the phrase was only needed for women and widower is a much later literary invention.

Widow had a lot of legal implications for property, titles and so on. If the survivor of a marriage was a woman things got complicated before women had many rights.
If the survivor was a man in the middle ages it didn't really make much difference as he held all the property anyway.

A similar question came up about illegitimate girl children, there was no word because there was no legal need to consider them.

For the rest - English generally doesn't have many genders anymore and those that have survived are where it was necessary to know the actual sex. So for example "actress" once had rather more of a euphemism role (like the modern 'model actress whatever') — where knowing their sex is relatively important.