Tam hats were popular back in the early 1900s and they hit the fashion scene in a major way back in the 1980s. Rumor has it that with the retro trends, tam hats are back on the scene.
This crochet and knit pattern for a tam hat was originally published in 1906. You begin with crochet and then switch to working the pattern in knit and purl.
Source: Evening star. [volume] (Washington, D.C.), 21 Oct. 1906.