I found this line in Hamlet by William Shakespeare.
I'll do't. Dost thou come here to whine?
What does "do't" mean? Google returneth only "don't". Is "do't" an alternative spelling of "don't"? Is "I'll don't" a common phrase in English?
See this link. "I'll do't" means "I will do it". It's not an alternative spelling of don't. Early English uses a lot more contractions in writing, and plays, especially Shakespeare's plays, use a lot because they're written in verse and need to shorten words and phrases to maintain the meter.