LSJ s.v. kegxrami/s records the sense of "olive kernel" only in this passage. The sense "fig seed" is found in: Hippocrates, De Natura Mulierum 109; Aristotle, History of Animals 549a (describing the size of a small crawfish egg); and often in Theophrastus and medical authors.
The singular is glossed in Hesychius kappa1963 as "the interior of the seed of a fig", but elsewhere Hesychius also uses the word to describe grains of wheat, suggesting it was becoming a generic word for "seed"; this is confirmed in Lampe s.v. kegxremi/s: "millet seed, hence any fine grain". Nevertheless, the Suda (in an excerpt from John Philoponus) still distinguishes between fig kegxrami/des and olive purh=nai at kappa 416.