There wasn’t a term to refer to the Holo language collectively, except I guess for the word Holo, which came from Hoklo, an exonym that the Hakka used derogatorily, so it’s not hard to imagine why this term wasn’t adopted earlier on.
Every Holo language just referred to themselves by the place of origin, like Tsuân-tsiu-uē, Tsiang-tsiu-uē, Amoy, Teochew, Lán-lâng-uē (Filipino), and so on. You may consider them all the same, but Tsuân-tsiu-uē, Tsiang-tsiu-uē, Amoy, Teochew are all different, and historically they do not consider themselves the same peoples speaking the same language, hence all the ethnic violence in Taiwan during the Qing rule.
The term Taigi (Taiwanese) is also an exonym, one coined by the Japanese, and it wasn’t until having a common enemy, the Japanese, and being treated the same by them, that Tsuân-tsiu and Tsiang-tsiu immigrants eventually forged a common Taiwanese identity.
You can see this in the names of the dictionaries around the same time:
Chinese–English Dictionary of the Vernacular or Spoken Language of Amoy, with the Principal Variations of the Chang-chew and Chin-chew Dialects (1873) – Carstairs Douglas and Thomas Barclay
Taiwanese Language Phrase Book (臺灣語集) (1895) - Matano Yasukazu
Taiwanese Phrase Book (臺灣言語集) (1895) - Iwanaga Rokuichi
A Collection of Taiwanese Phrases (臺灣會話編) (1895) - Sakai Hachigorō
Introduction to the Taiwanese Language from the New Territory of the Great Japanese Empire (大日本新領地臺灣語學案內) (1895) - Kato Yutaro
Taiwanese Language (臺灣語) (1895) - Tanaka
Complete Japanese-Taiwanese Phrase Book (日臺會話大全) (1896) - Mizukami Umehiko
Comprehensive Taiwanese–Japanese Dictionary (1931) – Naoyoshi Ogawa