sandhi form
Analysis. tasmā + iha: tasmā is the ablative of tad (that, it), meaning 'from that, therefore'; iha is the locative adverb meaning 'here' or 'in this regard'. The compound emphasizes reason and immediate application: 'for that reason, in this context'.
Etymology. tasmā from the demonstrative pronoun tad (Sanskrit tat, Latin id 'that'), cognate with English 'that'; iha from the locative stem meaning 'in this place', related to Sanskrit iha and the demonstrative root *i-. Together they form a common Buddhist formulaic phrase linking causality to present circumstance.
Meanings from the Digital Pāḷi Dictionary; morphology and etymology by Claude.
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