Originally, the word "herpes" (<G. "to creep") referred to any spreading skin lesions, spanning from ulcerative lesion to even skin cancers.

Without knowledge of viral etiology, old researchers classified many of these skin lesions under "herpes" category.

At that time, they used words like "herpes simplex," "herpes miliaris," "herpes exedens," "herpes syphiliticus," and so on.

Probably early physicians used the word "simplex" as a counterpart of other descriptors like miliaris, etc.

Herpes simplex originally meant just an ulcerative skin lesion until Gruter and Lowenstein showed its viral etiology in 1910-1920s.

Reference
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1034725/pdf/medhist00166-0018.pdf


Sorry, my computer doesn't let me type in Hangul..