A tassel is generally a tuft of wool, or other thread used as a decoration on cushions, scarves etc. Some plant heads or flowers are also refered to as tassels, if their stamens or other parts appear tassel like. Young sweetcorn cobs are an example.
A tassel can also refer to a piece of wood or stone supporting a joist or beam.
Jackie Sayle indulged in a spot of tasselling when she created my druid initiate*, as she tasselled yarn for the hair. She makes lots of brilliant knitted characters which she sells to raise money for a charity which helps people with cancer.