*gel-

The core idea of this root was:

cold, freezing

It’s the origin of many words that are about the idea of cold. 
Also, it’s the origin of Latin  gelare, which meant to freeze, to congeal and which is the origin of words like congeal, glacier and jelly.

Here’s an overview over the relatives in English.

• cold
• cool
• chill
• congeal
• gelato
• gelatine
• jelly
• glacier, glacial