The use of `` and '' comes from the typewriter days. You’ll see it particularly with professional authors who have been writing for print since then. See https

The use of `` and '' comes from the typewriter days. You’ll see it particularly with professional authors who have been writing for print since then. See https://en.wikipedia.org/wiki/Grave_accent#As_surrogate_of_apostrophe_or_(opening)_single_quote https://en.wikipedia.org/wiki/Grave_accent#As_surrogate_of_a... US QWERTY keyboards like the author is almost certainly using have the backtick above the Tab key, shared with ~, and it’s commonly used in programming.