[dgoldstein0]

So I looked up and discovered that bicycle helmets became a common thing in the 1970s. Perhaps motorcycles were earlier. But either way I have to ask - what did people wear helmets for in 1909? Im thinking that most helmet usage came later.

[defrost]

Helmet usage, as in protective headware for general melee war and one on one fighting, dates back to the bronze age.

Hard hats, of assorted kinds for general protection while working, date back to the 1890s and became more commonplace ~1920 (ish) onwards in construction, mining, and ship building industries.

* Helmets: https://www.battlemerchant.com/en/blog/the-evolution-of-hist...

* Hard Hats: https://en.wikipedia.org/wiki/Hard_hat

I suspect there are more early European hard hat examples to be found than are cited in the wikipedia article.

[pgreenwood]

I think they were fairly common for things like gladiatorial games, jousting, etc.