genieken, re-reading your rhyme, I'm stuck on the phrase "rank tank tank". There may be no connection at all, but it occurred to me that I had read that phrase "ranky tank" before.

Bessie Jones, the primary informant for the early 1980s book Step It Down: Games, Plays, Songs and Stories from the Afro-American Heritage {co-authored by her and Bess Lomax Hawes} refers to the "ranky tank" as a dance and {if I recall correctly} a somewhat risque dance that children did in the Georgia Sea Isles when she was a child.

I really have to purchase this book again as I've misplaced my copy. But here's a brief description that I found online:

"ranky tank-Excerpt - on Page 45: " ... one and two (rest), as in the fox trot. (See the dance by the same name for a fuller description.) RANKY TANK. Dance teachers would refer to this as a "buzz step"; the actual motion is rather like riding a scooter. ... "
http://www.amazon.com/phrase/ranky-tank

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Here's another online reference to Bessie's Jones' remembrance of the "ranky tank" dance:

"Step It Down weaves together the lyrics, music, and description of traditional Afro-American children's songs as well as Jones's comments on their meaning and "feel." Whether reciting "Tom, Tom, Greedy Gut" or demonstrating the more complex steps of "Ranky Tank" and "Buzzard's Lope," Bessie Jones always viewed the amusements of the young as preparation for adult roles and relationships, and as a teacher, she developed her own philosophy of how a black child is socialized into the larger community"
folkstreams-ranky tank

-snip-

These definitions are included among other meanings of the word "rank"

[adjective] very fertile; producing profuse growth; "rank earth"

[adjective] very offensive in smell or taste; "a rank cigar"

[adjective] conspicuously and outrageously bad or reprehensible; "a crying shame"; "an egregious lie"; "flagrant violation of human rights"; "a glaring error"; "gross ineptitude"; "gross injustice"; "rank treachery"
Synonyms: crying, egregious, flagrant, glaring, gross

[adjective] complete and without restriction or qualification; sometimes used informally as intensifiers; "absolute freedom"; "an absolute dimwit"; "a downright lie"; "out-and-out mayhem"; "an out-and-out lie"; "a rank outsider"; "many right-down vices"; "got the job through sheer persistence"; "sheer stupidity"
Synonyms: absolute, downright, out-and-out, right-down, sheer

[adjective] growing profusely; "rank jungle vegetation

http://www.elook.org/dictionary/rank.html


-snip-

Given those definitions, a social dance could be considered "rank" if the dancers moved in what some people would consider sexually suggestive ways. "Tanked" might refer to dancing down to the ground in time to the beat of the chant.

But I hasten to repeat that there may be no connection at all with the rhyming phrase "rank tank tank" in the "hanky panky" rhyme and the dance Bessie Jones recalls called the "ranky tank". That said, the term hanky-panky can have a sexual meaning of its own, can't it?

Be that as it may, I wanted to note this reference to the ranky tank dance just for the record.