Abarim Publications' online Biblical Hebrew Dictionary
צוץ ציץ
The forms צוץ (sus) and ציץ (sys) yield a small cluster of words that all have to do with flowers and blossoms. But other than in English, the Hebrew idea of a blossom is that of a temporary and intermediate form that must lose its shiny, attractive petals in order to become a seed bearing fruit.
This blossom principle occurs all over nature, from a star that shines until it loses its corona and becomes a black hole, to an explosion in bio-diversity followed by a mass extinction that wipes out weaker forms and establishes the forms upon which the whole biosphere will be continued.
Note that the blossom-phase produces nectar which attracts mostly dim-witted insects (and besotted poets), whereas fruits attract hungry mammals and birds and such (and note that the blossom principle also describes economic bubbles and hyperwaves).
צוץ I ציץ
The verb צוץ (sus I) or ציץ (sys) means to bloom or blossom (Psalm 103:15, Isaiah 27:6, Ezekiel 7:10) and is on rare occasions also used to mean to shine or gleam (of a crown: Psalm 132:18). Note that a similar duality exists in the verb קרן (qrn), meaning to radiate or have horns.
The sole derivation of this verb is the masculine noun ציץ (sis), meaning flower or blossom (Numbers 17:8, Isaiah 40:7, Job 14:2, 1 Kings 6:18). In Leviticus 8:9 and Exodus 28:36 this word denotes an element of the high priest's outfit, probably a crown or flower like item.
צוץ II
The verb צוץ (sus II) occurs only once, and it's not clear what it means (or even whether it's truly a separate verb). It occurs in Song of Solomon 2:9, where the groom appears to be peering through the lattice — possibly dropping the petals of his intuition and forming a solid conclusive fruit. The word translated with lattice is also a mystery, and this whole statement is extrapolated from the previous. It could mean something wholly else; we're clueless.
ציץ
The masculine noun ציץ (sis) is identical to the previous one meaning blossom or flower, but it's formally not clear if and how it relates to the above. It's used solely in Jeremiah 48:9, which literally speaks of a "blossom" being given to Moab for it to "fly" away. Here at Abarim Publications we surmise that this statement refers to the blossom principle, and that Moab will lose its attractive petals only to become a seed bearing fruit.
ציצת
The feminine noun ציצת (sisit) occurs in two contexts, and denotes a small bundle of hair: either a tassel on a garment (Numbers 15:38-39), or a lock of hair on one's forehead (Ezekiel 8:3). It's not clear how, precisely, this word relates to the previous, but there are obvious similarities between a flower and a tassel.