Glom, an American word with Scots and ultimately Gaelic origins, originally meant grab, snatch, or steal, and it often took the preposition onto. In more recent usage, however, the phrasal verb glom onto is usually used to mean to attach oneself to or associate oneself with. No one knows why glom took this new meaning, but it could be that glom‘s similarity to glue and gum gives it a sticky sound.
Glom is still used to mean steal or grab, but usually without onto.
The old glom was common as recently as the 1950s and 60s—for example:
Thanksgiving has been a time for a pause to take stock of the past twelve months and glom onto as much turkey as possible in one sittin’. [Prescott Evening Courier (1951)]
The pickpockets glom purses, the badger game obtains, minor stickups continue. [Sarasota Herald-Tribune (1957)]
King Hussein of Jordan asks how he can restore the Walls of Jericho when so many missing pieces continue to be glommed onto by the British museum. [The Southeast Missourian (1963)]
But now the newer sense of glom, usually used in the phrase glom onto, prevails—for example:
Young, up-and-coming teams tend to glom onto young, up-and-coming coaches. [The Cheap Seats]
The Koch brothers provided the Left with a convenient stereotype … to glom onto the Tea Party to discredit it. [Washington Examiner]
And the old sense of glom is rare but has not disappeared, though it no longer takes onto (glom onto now means exclusively attach to or associate with)—for example:
The revenue generating part of the business – sales and trading – has glommed all the glamour, all the publicity, and all the assets. [Fortune]
Two touchy-feely crooks bear-hugged a woman and then glommed her iPhone on Greene Avenue on Sept. 20. [Brooklyn Paper]