Como dizer "Cair em desuso" em inglês

And there is "to fall into/in disuse" in English as well:

These are words (or meanings) falling into disuse.

Regards

To fall out of favo(u)r

This style of house has fallen out of favor with most people lately. The Free Dictionary

Dependendo do contexto ...

Obsolete: no longer used because sth new has been invented

With technological changes many traditional skills have become obsolete.

Out of date: Out of style or use
These figures are very out of date.
Suddenly she felt old and out of date.
an out-of-date map
out-of-date technology

Old-fashioned:(sometimes disapproving)
not modern; no longer fashionable, dated

old-fashioned clothes/ styles/ methods/ equipment

Out-dated: no longer useful because of being old-fashioned
outdated equipment
These figures are now outdated.
It is an outdated and inefficient system.


Oxford Advanced Learner's Dictionary/The Free Dictionary