Actually, I still do see North Pacific and South Pacific in OSM Americana. The docs suggests that that is coming from OMT and then Natural Earth (at low zooms) or OpenStreetMapData (higher), but the OMT documentation is a little vague about what the ultimate source is (experience would suggest OSM nodes rather than relations, but it’d be nice to see the code).
“eo” is Esperanto. OSM oceans were afflicted for a while by a pest that insisted on using Esperanto for “international” names. See also here. Their logic was that English shouldn’t have a “special place” in OSM as it was just one language among many, and depending on how you count it may not be the most spoken. However, English does have a special place in “the language of the sea”, mainly for historical reasons.
I used Esperanto in my example as a bit of a joke because of that.