The word 'fern' is not a Welsh word and has no meaning. The Welsh word for 'a fern' is 'rhedynen'.
The Welsh word for Excellent is ardderchog, it is also the welsh for fantastic.
The Welsh word for mum is mam.The Welsh word for dad is dad.
the welsh word for trust is 'ymddiried'
The Welsh word for Toxic is: Gwenwynig
The Welsh word for 'landowner' is 'tirfeddiannwr'.
The Welsh word for 'a cave' is ogof.
The Welsh word for thunder is "taranu."
The Welsh word for 'rectangle' is petryal.
The Welsh word for Epiphany is Ystwyll.
The Welsh word for 'phoenix' is ffenics.
The name could be Welsh or maybe Scottish. Found this online: "Anglicized form of the Welsh family name Gwalchmai, which is from the Welsh personal name Gwalchmai 'hawk of the plain'" at this link: http://www.ancestry.com/facts/Gwaltney-name-meaning.ashx