What is the origin and meaning of the suffix -late, as in "isolate" and "desolate"?

I am sure that the word late as in tardy does not have the same origin. It certainly does not correlate with the terms.

I wonder if the actual suffix is closer to "olate" given my aforementioned terms.

Solution 1:

The suffix involved is '-ate', and it reached the English nouns (or adjectives) by two different routes. OED gives '-ate' in 'isolate' as

-ate, suffix¹

....

2. In some words, -ate = French -ate, < Latin or Italian -āta, as in pirate, frigate.

'Isolate' reached English from Italian isolato (and French isolé), themselves deriving from Latin insulātus.

For 'desolate' (noun and adjective), the route was more directly from Latin dēsōlātus, past participle of dēsōlāre.

The verbs 'isolate' and 'desolate' also differ significantly, etymologically speaking. 'Desolate' was formed on the model of the adjective, and first occurs much later than the adjective. 'Isolate' is a back-formation from the adjective or derives from French isoler (itself from Italian isolare, which is from Latin insulāre), plus the verb suffix '-ate'.

That's all very tortuous and, as you probably gathered from mention of 'pirate' and 'frigate', the bare meaning of the suffix is not especially germane to the conglomerative meaning of the terms. More germane is the meaning of the Latin stem that gave rise to 'isolate' and 'desolate', that is, sol, meaning "alone, only".

Solution 2:

The suffix in words desolate and isolate is not late at all; it's -ate(1) in adjective desolate and -ate(2) in verb isolate as explained in the Online Etymology Dictionary.

-ate (1): word-forming element used in forming nouns from Latin words ending in -atus, -atum (such as estate, primate, senate). Those that came to English via Old and Middle French often arrived with -at, but an -e was added after c. 1400 to indicate the long vowel. The suffix also can mark adjectives formed from Latin past participals in -atus, -ata (such as desolate, moderate, separate); again, they often were adopted in Middle English as -at, with an -e appended after c. 1400.

-ate (2): verbal suffix for Latin verbs in -are, identical with -ate (1). Old English commonly made verbs from adjectives by adding a verbal ending to the word (such as gnornian "be sad, mourn," gnorn "sad, depressed"), but as the inflections wore off English words in late Old and early Middle English, there came to be no difference between the adjective and the verb in dry, empty, warm, etc. Thus accustomed to the identity of adjectival and verbal forms of a word, the English, when they began to expand their Latin-based vocabulary after c. 1500, simply made verbs from Latin past-participial adjectives without changing their form (such as aggravate, substantiate) and it became the custom that Latin verbs were Englished from their past participle stems.

isolate (v):

"to set or place apart, to detach so as to make alone," by 1786, a back-formation from isolated (q.v.). As a noun, "something isolated," 1890; from earlier adjectival use (1819), which is from Italian isolato or Medieval Latin insulatus.

isolated (adj):

"standing detached from others of its kind," 1740, a rendering into English of French isolé "isolated" (17c.), from Italian isolato, from Latin insulatus "made into an island," from insula "island". English at first used the French word (isole, also isole'd, c. 1750), then after isolate (v.) became an English word, isolated became its past participle.

Solution 3:

It's not really a -late suffix. Isolate comes from insulatus ("made into an island") and desolate from desolatus ("abandoned"). The -atus ending is just the past-participle ending in Latin, equivalent to our -ed.