Perhaps the more usual question about this word is how to spell it. The only pronunciation I have ever heard, as far as I remember, is ˈdesɪkeɪt. This stressing and vowel pattern leads people to think it should be spelt dessicate. It’s only those few of us with a knowledge of Latin who immediately see it as containing the adjective siccus ‘dry’, which explains its unexpected spelling.
But let’s return to the question of its pronunciation. Surprisingly, the OED tells us that until 1864 deˈsiccate was the only stressing given in dictionaries. The OED itself (in the second edition, 1989) still gives priority to the pronunciation dɪˈsɪkeɪt. I wonder if anybody alive actually says that, or indeed if there was anyone who still said it twenty years ago.
For the historical change in stress the OED refers us to contemplate. Shakespeare apparently stressed that word as we do today (ˈkɒntəmpleɪt).
When this is known, then to divide the times:Nevertheless, the OED tells us,
So many hours must I tend my flock;
So many hours must I take my rest;
So many hours must I contemplate;
So many hours must I sport myself;
So many days my ewes have been with young;
So many weeks ere the poor fools will wean:
So many years ere I shall shear the fleece:
So minutes, hours, days, months, and years,
Pass'd over to the end they were created,
Would bring white hairs unto a quiet grave.
Ah, what a life were this! how sweet! how lovely!
—Henry VI, Part III: II, 5
the orthoepists generally have conˈtemplate down to third quarter of 19th cent.; since that time ˈcontemplate has more and more prevailed, and conˈtemplate begins to have a flavour of age.The OED continues (in the second edition, 1989, still)
This is the common tendency with all verbs in -ate. Of these, the antepenult stress is historical in all words in which the penult represents a short Latin syllable, as acˈcelerate, ˈanimate, ˈfascinate, ˈmachinate, ˈmilitate, or one prosodically short or long, as in ˈcelebrate, ˈconsecrate, ˈemigrate; regularly also when the penult has a vowel long in Latin, as ˈalienate, ˈaspirate, conˈcatenate, ˈdenudate, eˈlaborate, ˈindurate, ˈpersonate, ˈruinate (Latin aliēno, aspīro, etc.). But where the penult has two or three consonants giving positional length, the stress has historically been on the penult, and its shift to the antepenult is recent or still in progress, as in acervate, adumbrate, alternate, compensate, concentrate, condensate, confiscate, conquassate, constellate, demonstrate, decussate, desiccate, enervate, exacerbate, exculpate, illustrate, inculcate, objurgate, etc., all familiar with penult stress to middle-aged men. The influence of the noun of action in -ation is a factor in the change; thus the analogy of ˌconseˈcration, ˈconsecrate, etc., suggests ˌdemonˈstration, ˈdemonstrate. But there being no remonstration in use, reˈmonstrate, supported by reˈmonstrance, keeps the earlier stress.
Except that nowadays remonstration is in use, and the stress pattern ˈremonstrate has accordingly become usual (in BrE at least). The OED acknowledges this, commenting in its third edition (2009) as follows.
N.E.D. (1906) gives the pronunciation as (rĭmǫ•nstreit) /rɪˈmɒnstreɪt/, but in O.E.D. (ed. 2, 1989) this is marked as being ‘older’ and a pronunciation with first-syllable stress is given as the dominant one. Editions of D. Jones Eng. Pronouncing Dict. up to and including 1963 record the pronunciation with stress on the second syllable as the dominant one, and this is still indicated as an alternative pronunciation even in British English in subsequent editions.True. But nowadays we’re fed up with football managers who ˈremənstreɪt with the referee. Aren’t we?