The word "most spleenful" is not a commonly used term, but it can be broken down phonetically as /məʊst spliːn.fʊl/. The "məʊst" phonetically represents the sound "m-oh-st", while the "spliːn" is pronounced as "spleen" and the "fʊl" part is pronounced as "full". The word "spleen" refers to one's bad temper, bitterness or ill-temperament. Therefore, the term "most spleenful" would refer to someone who is extremely ill-tempered, filled with bitterness or experiencing anger.
The word "spleenful" is a relatively rare term that is derived from the noun "spleen". The term "spleen" comes from the Latin word "splen", which in turn originates from the Greek word "splēn".
The word "splēn" in Greek was used to refer to both the physical organ spleen and the metaphorical concept of melancholy or ill temper. This metaphorical sense of "splēn" was transferred to English in the 16th century and started being used to describe someone who is irritable, ill-tempered, or full of anger.
The adjectival form "spleenful" is formed by adding the suffix "-ful" to "spleen", turning it into an adjective to describe something or someone characterized by spleen or full of spleen.