I don’t know why, I just love the way it sounds and what it means. The main one definition, really is the large travelling bag made of stiff leather, I found that one a lot on line. But the definition
that makes me love the word is the one below, from dictionary.com:

Portmanteau

[pawrt-man-toh, pohrt-; pawrt-man-toh, pohrt-]

noun
1. a new word formed by joining two others and combining their meanings; “‘smog’ is a blend of ‘smoke’ and ‘fog'”; “‘motel’ is a portmanteau word made by combining ‘motor’ and ‘hotel'”; “‘brunch’ is a well-known portmanteau” [syn: blend]
2. a large travelling bag made of stiff leather