Short answers, pulled from the story.
The Sanskrit word hīnayāna literally means Small Vehicle or Lesser Vehicle. It combines the adjective hīna meaning little, poor, inferior, abandoned, deficient, or defective with the noun yāna which translates to vehicle.
Scholar Jan Nattier suggests the term Hīnayāna postdates Mahāyāna by a significant margin and emerged later due to antagonism between Bodhisattva and Arhat ideal proponents within the Sañgha. Early Mahāyāna texts rarely use the term Hīnayāna at all because it appeared as a back-formation only after attitudes toward the Bodhisattva ideal became critical.
Modern Buddhist scholarship has deprecated the term as derogatory and polemical so scholars now prefer Nikāya referring to the early Buddhist schools instead. Isabelle Onians asserts the preponderance of this name in secondary literature is far out of proportion to occurrences in Indian texts while Jonathan Silk argues Hinayana was used to criticize whomever one wanted on any given occasion.
Yijing wrote about four principal schools of continuous tradition existing in the West during the seventh century including Mahāsāñghika Nikāya, Sthavira nikāya, Mūlasarvāstivāda Nikāya, and Sañmitīya Nikāya. He stated which school grouped with Mahāyāna or Hīnayāna was not determined by these classifications.
Theravada would not have been considered Hinayana because it does not claim existence of independent dharmas and the concept of bodhisattva putting off enlightenment has no roots in Theravada textual contexts. Some contemporary Theravadin figures indicate a sympathetic stance toward Mahayana philosophy found in Heart Sutra while David Kalupahana holds that Mahayanists endeavored to preserve early teaching by emphasizing śūnyatā doctrine.