PAL

Ptolemaeus Arabus et Latinus

_ (the underscore) is the placeholder for exactly one character.
% (the percent sign) is the placeholder for no, one or more than one character.
%% (two percent signs) is the placeholder for no, one or more than one character, but not for blank space (so that a search ends at word boundaries).

At the beginning and at the end, these placeholders are superfluous.

demonstratio ‘proof’

Latin. – Grammar: n.

References: Alm. Gerard: I.1:14, f. 1vb:17
Translation of:
Arabic: برهان [Alm. MS Leiden: I.1:14, f. 2v:39]