punctuation space

Etymology
Used to give consistent presentation of quotation marks irrespective of comma or period placement.

Noun

 * 1)  A  of non- width: ⊣ ⊢ equal to the width of a   or, inserted after ⟨“⟩ or ⟨‘⟩ and before ⟨”⟩ or ⟨’⟩ (and sometimes ⟨?⟩ or ⟨!⟩), unless a  occurs there. It is Unicode character U+2008. When using X11 input method, the conventional key combination is Compose+Space+Period.
 * Many examples occur on page 204 of the 1837 New Sporting Magazine XIII.