Soteriology, soteria (salvation) plus logos (study), entered systematic theology in the 19th century as the doctrine-division covering atonement, grace, justification, and glorification. Every major tradition then back-filled the field: Buddhist, Hindu, and Islamic 'soteriologies' are now standard comparative-religion vocabulary.
The skeptical reading: soteriology is where religions itemize what is wrong with you and price the fix. Sin, karma, ignorance, the diagnosis varies; the structure, diagnosis, cure, terms, is the invariant product.
The question the '-ology' keeps open: rescue implies a destination. Christian versions aim at union or heaven; Buddhist versions at release; the Greek civic root aimed at intact survival. Soteriology's deepest disagreement is not about method but about what 'safe' means.
Can you diagram rescue without killing it?