It is quite clear that the word "signify" is derived from sign and the suffix -ify:
- sign + -ify = signify
The letter "g" in the word sign is silent but when the suffix is added, it becomes pronounced:
Although the "g" doesn't get pronounced when another suffix -able is added:
- sign + -able = signable ... /ˈsaɪnəbəl/ (no /g/)
Another example is the word damnify:
Upon the addition of the suffix -ify the "n", which would otherwise be silent, becomes pronounced. Now I looked up their etymologies and came to know that those words weren't formed within English. "Damnify" is from Old French damnefier and "signify" is from Old French signifier and I suspect they have etymological /g/ and /n/, respectively.
For "signable" Wikitionary merely says "sign + -able" and I can't find it in any other etymological dictionary. The reason "signable" doesn't have a /g/, in my opnion, can be attributed to its compounding within Modern English; looking at the results from Google Ngram makes my opinion appear correct in that "signable" has zero results and "signify" predates it by over 500 years.
The suffix -ify (which we also use to make words in Modern English) is from French ifier.
I have two closely related questions:
- Does the suffix -ify have any inherent characteristic of making consonants pronounced which would otherwise be silent?
- What if I add it to a Modern English word (say benign or align)? Will it make the "g" pronounced?