FoMo
Fomo is anxiety that an exciting or interesting event may currently be happening elsewhere, often aroused by posts seen on a social media website. Sufferers of FOMO might buy crypto based on emotion.
haha, it is not an "anxiety" or... FOMO (all caps) is simply an abbreviation of the term "fear of missing out". it usually refers to those who perform panic buying after the price starts going up instead of before.
Bagholder
A Bagholder is a person who purchases Bitcoin at the top of the market. It also refers to altcoins, many of which are pump-and-dump schemes.
the "bag" in "bagholder" refers to "garbage" otherwise it is simply a "holder" or "a long term investor" for example when you buy real estate, stocks, gold,... and don't sell it for years they can't call you a "bagholder" but when you buy garbage and hold it (such as altcoins) then you become a bagholder.