We found an old Chinese/Hawaiian cookbook with a section on this main ingredient. But Googling fails. Any insight from the teeming millions?
I’m guessing Jicama, based on this and a few other articles:
Aliases — Mexican turnip, Mexican water chestnut, potato bean, yam bean, yam bean tuber; sar-gott, 豆薯 (CHINA); sinkama (FILIPINO); dolique bulbeuse (FRENCH); bengkuang (INDONESIAN); chicam, štšikam, tšikam, xicam (MAYA); jícama (NAHUATL); củ đậu {meaning: bean root}, củ sắn (VIETNAM);
Without knowing more from your cookbook though, it’s just an informed guess.
This PDF shows mentions it as an “oriental vegetable in Hawaii” on page 60 by that name as well.
Wiktionary seems to concur that it’s the Cantonese word for jicama.
https://en.wiktionary.org/wiki/沙葛
The cookbook was published by the Chinese Committee International institute YWCA Honolulu, 1941:
(And Jesus, am I fighting spellcheck to transcribe this!)
Sar Gott Chop Suey
Sar Gott, sliced (there’s your clue)
Bamboo shoots
Sliced ham
“Chinese (snow?) peas
Celery, sliced
Pork, sliced
Green onions
“Chinese” parsley (cilantro?)
Peanut oil
Oyster sauce
Garlic
Okay, the Wikipedia article on Jimcama, though it makes no mention of “sar gott,” (and it doesn’t have a baseball/besabaru” sound similarity) does describe it as a legume where the tuber has great value (though no mention of the beans), transported by the Spanish from Mesoamerica to the Philippines, and used as a primary ingredient for lumpia.
(Once you’ve had lumpia, you’ll never accept any egg roll)
As a primary ingredient in some recipes for lumpia, anyway.