According to Beekes, probably from Pre-Greek as there's no connection with other words.
The ι is short in some sources and long in others, thus:
or
σῑ̆ρός • (sīrós) m (genitive σῑ̆ροῦ); second declension
Case / # | Singular | Dual | Plural | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Nominative | ὁ σῑ̆ρός ho sīrós |
τὼ σῑ̆ρώ tṑ sīrṓ |
οἱ σῑ̆ροί hoi sīroí | ||||||||||
Genitive | τοῦ σῑ̆ροῦ toû sīroû |
τοῖν σῑ̆ροῖν toîn sīroîn |
τῶν σῑ̆ρῶν tôn sīrôn | ||||||||||
Dative | τῷ σῑ̆ρῷ tôi sīrôi |
τοῖν σῑ̆ροῖν toîn sīroîn |
τοῖς σῑ̆ροῖς toîs sīroîs | ||||||||||
Accusative | τὸν σῑ̆ρόν tòn sīrón |
τὼ σῑ̆ρώ tṑ sīrṓ |
τοὺς σῑ̆ρούς toùs sīroús | ||||||||||
Vocative | σῑ̆ρέ sīré |
σῑ̆ρώ sīrṓ |
σῑ̆ροί sīroí | ||||||||||
Notes: |
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