liminal (adj.)

c. 1400, "boundary, frontier," from Old French limite "a boundary," from Latin limitem (nominative limes) "a boundary, limit, border, embankment between fields," which is probably related to limen "threshold," and possibly from the base of limus "transverse, oblique," which is of uncertain origin. Originally of territory; general sense from early 15c. Colloquial sense of "the very extreme, the greatest degree imaginable" is from 1904.

suffix forming adjectives from nouns or other adjectives, "of, like, related to, pertaining to," Middle English -al, -el, from French or directly from Latin -alis (see -al (2)).