A frequentative is a word that indicates that an action is done repeatedly. While frequentatives are common in many languages, including Hungarian, Finnish, and Latin, English does not currently have a regular frequentative form. We do have a number of 'leftover' frequentatives from Middle English and related languages. These words most often end with -le and -er, but many past frequentatives have lost their original meanings.
Fully mutated frequentatives include 'slumber', which was the frequentative of slumen, meaning 'to doze'; 'fondle', the frequentative of fond, meaning 'to dote'; 'trample', the frequentative of 'tramp'; 'scuffle', from 'scuff'; 'jiggle', from 'jig'; 'dabble', from 'dab'; and 'haggle', from haggen, meaning 'to chop'... along with dozens of others.
However, a number of words have kept something like their original sense, and remain frequentative in nature. These include: 'tinkle', the frequentative of tinken, 'to ring'; 'scrabble', from schrabben, meaning 'to scratch'; 'bicker', from bikere, meaning 'to fight'; 'bobble', from 'bob'; 'nuzzle', from 'nose', (as in a dog or pig nosing the ground); 'sizzle', from the Middle English sissen, meaning 'to hiss'; 'whittle', from the Middle English þwitan, meaning 'to cut'; 'dribble', from 'drip'; 'crinkle' from Old English crincan, meaning 'to bend'; skitter from skite, meaning 'to run quickly'; and 'sparkle', the frequentative of 'spark'.
It is interesting to note that English used the frequentative to generate new words well into the 1800s, including 'bobble' in 1812, 'sniffle' in 1819, 'tootle' in 1820, 'jiggle' in 1836, and 'skitter' in 1845. By the end these were clearly informal and perhaps even slightly silly words, but were recognizable and useful enough to catch on in common usage. I have not been able to find a clear example of familiar frequentative coined after 1850, but I would be interested if anyone can identify one.