Vellication

Where irritation coincides with sensation to produce the same catenations of motion, as in inflammatory fevers, they are excited with still greater energy than by the irritation alone. So when children expect to be tickled in play, by a feather lightly passed over the lips, or by gently vellicating the soles of their feet, laughter is most vehemently excited; though they can stimulate these parts with their own fingers unmoved. Here the pleasureable idea of playfulness coincides with the vellication; and there is no voluntary exertion used to diminish the sensation, as there would be, if a child should endeavour to tickle himself.

Source: wiktionary

The sense of itching, which may be defined a painful titillation local or general, relieved by rubbing, is commonly a result of some mechanical or morbit irritant applied externally or internally to the part affected; though sometimes, unquestionable, dependenat upon a morbid sensibility of the nerves feeling themselves. If the summit of the nerves or their extreme points be alone touched, the effect is tickling or titillation, as in the vellication of the skin by a feather.

Source: wiktionary

Dear Madam, I think it long ſince I wrote, and ſometimes venture to hope that you think it long too. The intermiſſion has been filled with ſpaſms, opiates, ſleepleſs nights, and heavy days. Theſe vellications or my breaſt ſhorten my breath; whether they will much ſhorten my life I know not, but I have been for ſome time paſt very comfortleſs.

Source: wiktionary