Key (of keyboard), Word
A key on a (computer, typewriter or even piano) keyboard has nothing to do with the key of a lock. English appears to be in a minority of languages in using the same word for both concepts; certainly, French and German have different words (touche, clé; Taste, Schlüssel).
The distinction is important, given that computers can have locks and keys, as well as keyboards and keys. I suggest "cnaipe" for keyboard key; "murlán" is also a possibility. I do not consider that the possible use of "cnaipe" for "screen button" in GUIs is a serious disadvantage; of the two, I think the keyboard key has the stronger call on the term "cnaipe", and another word can be found for "screen button" if that proves necessary (the Scots have "putan" for it).
Of course "key" has other meanings in computing. There is "record key" or "key field" as that field or fields of a record which distinguish each record of the type from all the others, and which can lead us to the required record. "Eochair" is more acceptable for this meaning of "key", but "treoir-réimse" is a more exact characterisation of the concept.
And there is "keyword", which contains two problematic elements, "key" and "word". In regard to "word", it has two meanings in computing. First, there is the normal meaning of a graphic unit of language, natural or programming; this is the meaning in "word processing", for example, and in "reserved word". The Irish for this is clearly "focal". Second, "word" is used for a unit of memory storage consisting of a fixed number of bits, often 16 or 32, and for which the term is "giotánra" (FR 347). However, there is a tendency to use "giotánra" in where "focal" should be used, one example which is still uncorrected being "word wrap" (FR 347, timfhilleadh giotánra).
Returning to "keyword", it has at least two meanings. Firstly, "keyword" can mean an index term in indexing or searching. For this I suggest "treoir-fhocal", though again "eochair-fhocal" would not be out of the question. "Keyword" has not been differentiated by sense in official terminology, and presumably this sense is the one intended there. "Eochairfhocal" has now become the official term (FR 255, for keyword). Previously, we had the erroneous "giotánra eochrach" (TR 133).
Secondly, "keyword" can mean a reserved word (e.g. in a programming language), carrying a special syntactic meaning and therefore unavailable to be put to any other use by the programmer. For this, I suggest "sain-fhocal". FR has "focal coimeádta" for "reserved word" (FR 306). TR had the erroneous "giotánra áirithithe" (TR 160) for "reserve [sic] word".