Learn English – Non-religious equivalent expression for “Pray for [Country X]” after a disaster

Aside from a hair-splitting distinction among some Catholics (see below), there is no official term, and you will find a variety of choices:

• layman's clothes is probably the most obvious way to make a distinction between clothes worn by clerics and clothes worn by non-clerics.
• More formally, one could refer to lay dress or lay costume, as a neat parallel to clerical dress or costume.
• More generically, at least in American English, street clothes are the ordinary clothes people wear in public, as opposed to specialized garments such as sportswear or work uniforms.
• You could borrow the term civilian clothes, in more casual usages; usually this term is used to contrast street clothes from a police or military uniform. The slang civvies may be suitable in some cases.
• As Josh61 has indicated, police who do not wear a uniform are plainclothes officers, or work in plain clothes.
• Rarer is conversation is mufti, already mentioned by bib. According to the Online Etymology Dictionary, this meaning is from 1816, of unknown origin, perhaps from mufti's costume of robes and slippers in stage plays, which was felt to resemble plain clothes.

In Catholicism, it depends on what you mean by religious attire. There are various various types of clerical dress for different purposes, and while the customary daily dress is the cassock, in many countries, at least among secular priests, the cassock has been replaced by the clerical suit.

This is not a newfangled development. The clerical suit was long preferred in Britain in order to distinguish Catholics from their cassock-clad Anglican cohorts, and in the U.S., it was adopted at one or the other Councils of Baltimore as a precaution amidst strong, sometimes violent anti-Catholicism in American society. But to some traditionalists, the cassock is the only acceptable public costume, and therefore the clerical suit is not "official" attire.

In English we have an expression that basically means someone is very healthy:

"fit as a fiddle" (which if taken literally, brings a strange picture to mind!)

According to the website knowyourphrase.com, the expression "fit as a fiddle" was used in the book "English-men for my Money", written in the year 1616 by Haughton William. Towards the end of the book, it reads:

"This is excellent ynfayth, as fit as a fiddle."

Another similarly alliterative expression is:

"healthy as a horse"