Origins
Remark is a Germanic word in French clothing. It comes from French remarquer — 're- + marquer' — meaning 'to mark again, to take notice of'. But marquer itself is not Latin. It comes from Frankish *markōn, a Germanic word meaning 'to mark' or 'to note', from Proto-Germanic *markō ('boundary, sign').
The original meaning of remark in English was not 'to say something' but 'to notice something' — to mark it again in the mind. Samuel Pepys wrote of 'remarking' curious sights, meaning he observed them closely. The shift to speech happened because pointing something out verbally is a way of marking it for others.
The Germanic root *markō had a concrete physical meaning: a boundary marker, a sign cut into a tree or placed at a border. From it English also gets mark, marker, and the noble title marquis (originally a lord who guarded the marches, the border regions). Even Denmark contains the root: it means 'the border-land of the Danes'.
Later History
Remarkable — meaning 'worthy of being noticed' — appeared in the mid-17th century and quickly became one of the most common English adjectives. Something remarkable demands a second mark on the mind; it refuses to go unnoticed.
The word's three-family journey (Germanic root, French reshaping, English adoption) is a common pattern in English vocabulary, where French often served as a bridge between Germanic and English.