The Spanish word "santiguar" means "to make the sign of the cross". So for instance, when a Catholic enters a church, s/he "se santigua" (s/he makes the sign of the cross on her/himself).
According to Wiktionary, this word comes from the Latin sanctifico, which means "to sanctify". In effect, according to link above, "santiguar" also means "to sanctify", which could explain its origin (I still have doubts though). In any case, nowadays, "santiguar" is no longer used to mean "to sanctify". There is a more direct Spanish word for it: "santificar". Thus, "santiguar" is used only to refer to making the sing of the cross.
My question is about how "santiguar" gained such meaning. Did it gain it already when the word was incorporated into Spanish, or does such meaning also comes from Latin? From what I can see, sanctifico does not mean "to make the sign of the cross". Actually, I've struggled to find how that is said at all in Latin! The sing itself is called signum crucis, but I can't find a verb that reflects the action of making such sign.
Any idea on this? I think looking for medieval religious texts might be key here. I did an early search and signum crucis is of course ubiquitous, but as a "noun" and not as a verb.