Douglas Harper's Etymology Dictionary
also spic-and-span, 1660s, from spick-and-span-new (1570s), literally "new as a recently made spike and chip of wood," from spick "nail" (see spike (n.1)) + span-new "very new" (c.1300), from Old Norse span-nyr, from spann "chip" (see spoon (n.)) + nyr "new." Imitation of Dutch spiksplinter nieuw "spike-splinter new."
Wiktionary
a. (context idiomatic English) clean, spotless; original sense “like new”.
WordNet
adj. conspicuously new; "shiny brand-new shoes"; "a spick-and-span novelty" [syn: brand-new, bran-new, spic-and-span]
completely neat and clean; "the apartment was immaculate"; "in her immaculate white uniform"; "a spick-and-span kitchen"; "their spic red-visored caps" [syn: immaculate, speckless, spic-and-span, spic, spick, spotless]
Usage examples of "spick-and-span".
Nothing dirty, smelly or unpleasant, just spick-and-span shiningness and wonder.