Stick is related to Stem. Stem is related to Neck. Neck is related to Fragile. Fragile is etymologically related to Fraction. 
Stimulate is a synonym of Provoke. Provoke is a synonym of Stir. Stir is a synonym of Disturb. Disturb is a synonym of Trouble. 
Stick <--RelatedTo--> Stem <--RelatedTo--> Neck <--RelatedTo--> Fragile --EtymologicallyRelatedTo--> Fraction 
Stimulate <--Synonym--> Provoke <--Synonym--> Stir <--Synonym--> Disturb <--Synonym--> Trouble 