How did 1 beneath semantically shift to 2? Etymonline:
1530s, abbreviation of videlicet [2.] "that is to say, to wit, namely" (mid-15c.),
from Latin videlicet, contraction of videre licet [1.] "it is permissible to see,"
from videre "to see" (see vision) + licet "it is allowed," third person singular present indicative of licere "be allowed" (see licence).
The -z- is not a letter, but originally a twirl, representing the usual Medieval Latin shorthand symbol for the ending -et. "In reading aloud usually rendered by 'namely.' " [OED]
The semantic shift for 'scilicet' looks similar, but I also don't understand it.