Siamon is not a popular first name. It is more often used as a boy (male) name.
First names and their meaning - Page 12237
Siân
Name day: 21 August. 
Siân (also Sian, Shân, Sharn, and Shan; pronounced [ʃɑːn]) is a Welsh feminine given name, equivalent to the English Jane, […] 
Siarhej
Siarhej is not a popular first name. It is more often used as a boy (male) name.
Siarhey
Siarhey is not a popular first name. It is more often used as a boy (male) name.
Siarl
Siarl is not a popular first name. It is more often used as a boy (male) name.
Sibb
Origin: Jewish. 
Sibb is not a popular first name. It is more often used as a girl (female) name. 
Sibbele
Sibbele is not a popular first name. It is more often used as a boy (male) name.
Sibe
Sibe is not a popular first name. It is more often used as a unisex (male and female) name.
Sibéal
Origin: Jewish. 
Meaning: Prophetess. 
Sibéal is not a popular first name. It is more often used as a girl (female) name. 
Sibele
Sibele is not a popular first name. It is more often used as a girl (female) name.