Indrasthāvarakāya is a nickname of the Pṛthvīkāya (earth-bodied beings), as the Pṛthvīkāya which is one of the sthāvarakāyas (Sthāvara Jīvas (living being incapable of undertaking locomotion)) is related to Indra (the king of the gods).
indrasaṃbamdhitvādindraḥ sthāvarakāyaḥ pṛthivikāyaḥ.
(Sthā 5.19 Vṛ Pa 279)
paṃca thāvarakāyā paṇṇattā, taṃ jahā- iṃde thāvarakāe, baṃbhe thāvarakāe, sippe thāvarakāe, sammati thāvarakāe, pāyāvacce thāvarakāe.
(Sthā 5.19)