etymologeek.com dictionary
English word functional comes from English function, English -al.

Functional etymology history?

Functional detailed word origin explanation

Dictionary entryLanguageDefinition
function English (eng) (intransitive) to carry on a function; to be in action. (intransitive) to have a function (anthropology) The role of a social practice in the continued existence of the group.. (biology) The physiological activity of an organ or body part.. (chemistry) The characteristic behavior of a chemical compound.. (computing) A routine that receives zero or more arguments and may return a result.. [...]
-al English (eng) (organic chemistry) Forms the names of aldehydes. Forming nouns, especially of verbal action.. Of or pertaining to. Adjectival suffix appended to various words, often nouns, to make an adjective form. Often added to words of Latin origin, but used with other words also.
functional English (eng) (computing theory) Having semantics defined purely in terms of mathematical functions, without side-effects.. (medicine) Of a disease, such that its symptoms cannot be referred to any appreciable lesion or change of structure; opposed to organic disease, in which the organ itself is affected.. In good working order.. Only for functional purposes, notably in architecture. Useful; serving a [...]

Words with the same origin as functional

Descendants of -al
additional approval arrival betrayal chemical confidential critical cultural disposal emotional historical identical lex logical magical mechanical mental political practical professional proposal rehearsal serial survival traditional