when and where is first occurence of word "zap" ? Online Etymology dictionnary mentions comic strip Buck Rogers but without any precise date or quotation
The term earliest appearance appears to be from 1929 as a noun. The comic strips “Buck Rogers in the Twenty-Fifth Century" were published from 1929 to 1967 and, apparently, used the term quite often.
(orig. US) an excl. used to describe the force of a sudden impact:
1929 P.F. Nowlan in Wash. Post 7 May 16/3: Ahead of me was one of those golden dragon Mongols, with a deadly disintegrator ray... Br-r-rr-r-z-zzz-zap.
(orig. US milit.) to kill, to defeat.
1942 [US] Berrey & Van den Bark - The American Thesaurus of SlAng.
Here is a strip from 1933 where the term zap as a verb is used: