17-year-old Helena Muffly wrote exactly 100 years ago today:
Monday, June 10, 1912: This morning I picked berries and helped myself to some. I wonder if anyone saw me. I want Ruth to help me with a jigger to-night, but I guess she doesn’t have the inclination to.
Her middle-aged granddaughter’s comments 100 years later:
I always think that eating strawberries is half the fun of picking them—but perhaps Grandma was being paid by a neighbor to harvest them. The previous year, on June 12, 1911, she wrote:
Started to pick strawberries this morning. Of course it will mean some early rising and loss of sleep, but just look at what I can earn.
I’m not sure what a jigger refers to in this entry, but one definition is a tool. Webster’s online dictionary mentions says that a jigger is a “small pointed metal instrument, resembling sharpened pencil, used in assembling ribs of expansion metal watch bands.” I don’t know if metal watchbands existed a hundred years ago, but if they did I can picture that Grandma may have had a watchband that needed adjustment.
A Hundred Years Ago 
Lots of other definitions of a jigger on wikipedia, but none of them stand out as something likely for your Helena to be needing help with, unless she got bitten by a flea while picking the strawberries 🙂
What a fun interpretation. 🙂
My first thought if jigger, from vague memories of my grandparents would be to help on fixing or using a devise that shook (jiggled) some foodstuff — but dinna make sense with strawberries. — but then I really dinna know — just adding my 2 cents worth.
Interesting that you have a vague memory of your grandparents actually using this term. It makes more sense to me than in relation to fixing watchbands.
Oh ! I love actually seeing her writing! 🙂
Finally remembered where I’d heard the term “jigger”… family story about using the “jigger” on the railway track which passed their house…A hand pumped sort of cart… Promise not to obsess over this one 🙂
Sometimes it’s fun to obsess a bit while trying to figure out the archaic meanings. 🙂
Could she have meant a jigsaw puzzle?