What is the meaning of こん?

事: thing

坤:

金: one of the five classical elements in traditional Chinese philosophy and medicine: see the "Wu Xing" entry on Wikipedia

根: perseverance, patience; (arithmetic) root

紺: navy blue, dark blue

喉: fish

献:

魂: soul

鯤: (Chinese mythology) a giant fish

今: this

今, 近: a surname

鯀: Gun (Chinese)

short for こんにちは

short for こんばんは

Source: wiktionary.org