yuánlái 原来 and běnlái 本来 can both mean ‘originally’, with the opposite meaning of ‘current’, but they are different in two aspects.
First, běnlái 本来 can be used to express the meaning of ‘It should be it in light of the certain reason.’ For example,
1)我本来想昨天给你，但是忘记了。
Wǒ běnlái xiǎng zuótiān gěinǐ， dànshì wàngjìle
I originally want to yesterday give you but forget
‘I meant to give it to you yesterday, but forget it.’
Under such circumstance, we is ungrammatical to use yuánlái 原来.
Second, , 原来 means ‘out of anticipation’. For example,
2)原来你的能力这么强，我以为你不会这些技能。
Yuanlái nǐde nénglì zhème qiáng， wǒ yǐwéi nǐ búhuì zhèxiē jìnéng
Originally your ability so strong I think you don’t know these skills
‘You are so capable, I mistakenly thought you didn’t have these skills.’
