I was editing an article about intermittent fasting (that is, not eating for all or part of a day, interspersed with normal (possibly restricted) eating on other days).
Inevitably, I got thinking about the various meanings of fast, as an adjective or adverb meaning quick(ly), as an adjective or adverb meaning firm(ly), secure(ly) and as a noun or verb meaning an abstention/to abstain from food. Dictionary.com doesn’t help. It lists the quick(ly) and firm(ly) meanings together, and notes that they are “akin to fast2” (that is, the noun/verb).
Etymology.com has possibly too much information. As I understand it, the firm, secure meaning came first. The abstain from food meaning came next, and means, basically, to hold oneself firmly. The quick meaning came last. If you run firmly, you run quickly. (Fast asleep means firmly, securely asleep, not quickly asleep, which might be confusing to young children, who almost certainly encounter the quick(ly) meaning first.)
From hold fast has come holdfast, which means a firm grip, a staple or clamp, or an organ by which an aquatic plant or animal can attach to a surface. Note also Holdfast Bay, Adelaide, South Australia, which got its name after Colonel William Light, the SA surveyor-general found anchorage there in a storm.
Hang on, though, I’ve encountered the meaning of a small fortress. But that appears to be used only in fantasy novels; Wikipedia’s disambiguation page gives GRR Martin’s A song of ice and fire series as an example.
PS At a funeral this afternoon, the word steadfast was used.