Recent change in pronouncing homage

The pronunciation most dictionaries list as most common is HOM-ij, with stress on the first syllable and with a sounded h. However, OM-ij and oh-MAHZH with silent h are becoming increasingly common.

Looking at the Google Ngram Viewer, it looks as though the pronunciation flipped around 1800 from silent h to what is now considered the traditional pronunciation.

But that also coincides with the approximate time English pronunciation began to be standardized—namely the advent of John Walker's A Critical Pronouncing Dictionary (1791) and Thomas Sheridan's A General Dictionary of the English Language (1780)—so it might be indicative of a prescriptive standardization rather than an actual immediate change in people's pronunciation.

From a 2010 New York Times article by Ben Zimmer:

While most U.S. dictionaries list HOM-ij first, one exception is Merriam-Webster’s Collegiate Dictionary. Joshua S. Guenter, Merriam-Webster’s pronunciation editor, explained to me that prior to the Tenth Edition of the dictionary in 1993, the pronunciation of homage was given with the initial “h” in parentheses, “indicating the two variants were about equally common.” Starting with the Tenth, they began giving a slight edge to OM-ij. “Our citation files do show the ‘h’-less variant to be more common than the ‘h’-ful one, though not by a huge degree,” Guenter said.

French /h/ had already disappeared by the time of the Norman Conquest, so /h/ in homage is indeed an English innovation, whether it was reintroduced only once or many times (probably the latter). Zimmer says:

As with many other imports from Norman French into Middle English, the initial “h” was not originally pronounced in homage. Eventually, so-called spelling pronunciation introduced the “h” sound to words like habit, host, hospital and human. Some words resisted the extra puff of aspiration, like heir, honest, honor and hour ... Starting around the eighteenth century, homage joined the “h”-ful crowd.

The pronunciation more faithful to French, oh-MAHZH, is apparently much more recent as Merriam-Webster seems to be the only dictionary that has caught up on it. It is generally confined to the relatively new sense of an artistic tribute, so, Zimmer argues, it may be understood as a reintroduction of French hommage, comparable to the way auteur is now re-borrowed into English, which refers to a filmmaker with a distinct style like Scorsese or Wes Anderson, not just any "author".

Zimmer concludes:

Listening to 10 recent uses of the word homage by on-the-air personalities [on NPR], I found an even split: five for oh-MAZH and five for OM-ij, with the latter generally reserved for the “respect” meaning, as in pay homage. The HOM-ij pronunciation, meanwhile, seems to be losing out to its trendier h-less rivals, despite the protestations of traditionalists. And since it’s a fight of two against one, “a homage” may, over time, become increasingly rare.