Origins
The word 'path' descends from Old English 'pæþ' (path, track, way), from Proto-Germanic *paþaz (path). The word is well attested in the West Germanic languages — Old Frisian 'pæþ,' Old Saxon 'pað,' Old High German 'pfad' (modern German 'Pfad'), Dutch 'pad' — but is absent from the North Germanic (Scandinavian) branch, which used 'stígr' (path, trail — related to English 'sty' in 'pigsty' and the verb 'stigh,' to climb) instead.
The deeper etymology of *paþaz is one of the long-running debates in Indo-European linguistics. The most frequently proposed connection is to PIE *pent- (to tread, to go, to find one's way), which is well attested in the Indo-Iranian branch: Sanskrit 'pánthāḥ' (path, road, way, journey), Avestan 'pantā' (way, path), Old Persian 'pathi-' (road). If this connection holds, then English 'path' and Sanskrit 'pánthāḥ' are genuine cognates separated by six thousand years of independent development. However, the phonological correspondence between Germanic *paþaz and Indo-Iranian *pant- is irregular, and some linguists prefer to treat the Germanic word as having no secure PIE etymology.
A competing theory derives *paþaz from a Scythian or Iranian source via early contact, treating it as a very old loanword rather than an inherited term. The West Germanic distribution (absent from North Germanic) could support this — a borrowed word might not have spread to all branches. But the evidence is circumstantial, and no consensus has been reached.
Old English Period
The Old English form 'pæþ' had a long vowel, and its plural was 'paðas,' with a voiced 'ð' sound between the vowels. This voicing alternation between singular and plural survives in Modern English: 'path' /pɑːθ/ (voiceless) versus 'paths' /pɑːðz/ (voiced), paralleling 'bath/baths,' 'mouth/mouths,' and 'youth/youths.' This alternation is a fossil of Old English phonology preserved in a handful of common words.
Compound words built on 'path' include 'footpath' (a path for walking, not riding or driving), 'towpath' (a path beside a canal or river, used for towing barges), 'pathway' (a path or its figurative extension), and 'pathfinder' (one who finds or makes a path through unknown territory). The figurative sense of 'path' as a course of action or way of life — 'the path to success,' 'the path of righteousness' — is ancient, attested in Old English and paralleled in virtually every language that has a word for a physical track.
One common trap: 'pathology' and 'pathetic,' despite their spelling, are entirely unrelated to 'path.' They derive from Greek 'pathos' (suffering, feeling, experience), from PIE *kwent- (to suffer). The resemblance in English is purely accidental — one of those hazards that a language with such a vast, multi-sourced vocabulary sets for the unwary.