This is a popular idiom and every human being have seen its worth in their life time. The idiom suggests that a past negative experience makes someone wary and less likely to repeat it, or to approach similar situations with the same level of confidence or enthusiasm. This popular idiom is well available in Hindi, and have been used very often. This time I comes across it's Sanskrit version which states :
दुर्जनदूषितमनसां पुंसां सुजनेप्य विश्वासः|
बालः पायसदग्धो दध्यापि फूत्कृत्य भक्षति||
Durjandooshitmanasaam punsaam sujanepya vishwashh.
Baalh paayasdagdho dadhyapi phootkrutya bhakshati.
Durjan = wicked person.
Dooshit = polluted.
Mansaam = mind.
Pumsaam = person(s).
Sujanepya = sujan + api
Sujan = noble person
Api = not even, doubts about.
Vishwaas = faith.
Baalah = a child.
Payas = milk pudding.
Dagdho = burnt by.
Dadhyaapi = even the curd.
Phootkrutya = the process of cooling a thing by blowing wind over it by using one's mouth.
Bhakshati = eats.
A person cheated by a wicked person does not have faith even in noble persons, just as a child having burnt his mouth while eating piping hot milk pudding, next time while eating curd (yoghourt) takes extra precaution of cooling it by blowing over it through his mouth.
We can use the phrase "once bitten, twice shy" to describe someone who is hesitant or cautious after a negative experience, or to explain why someone is avoiding a particular situation or activity.
In Hindi we call this as 'दूध का जला छाछ भी फूक फूक कर पीता है' i.e doodh ka jala chhachh bhi phoonk phoonk kar peeta hai. Buttermilk is called 'chhaachh' in Hindi.
