elasticsearch rails searching models - ruby-on-rails

Question

I am using elasticsearch-rails and elasticsearch-model gem for searching products in my rails app.
I want to make my search case insensitive and must be independent of pluralization. I researched a lot on google but got a hunch on how to do it using analyzer but not success. So I had to post a new question.
Here is my product model where I want to search to take place
class Product < ActiveRecord::Base
include Elasticsearch::Model
include Elasticsearch::Model::Callbacks
belongs_to :category
belongs_to :sub_category
has_many :variations
settings index: { number_of_shards: 1 } do
mappings dynamic: 'false' do
indexes :name, analyzer: 'snowball'
indexes :description, analyzer: 'snowball'
indexes :category, analyzer: 'snowball'
end
end
def as_indexed_json(options={})
as_json(only: [:name, :description, :brand, :color, :make, :style, :gender],
include: { category: { only: :name}, sub_category: {only: :name}}
)
end
def self.search(query)
__elasticsearch__.search({
query: { query_string: {
query: query,
default_operator: "AND"
}},
})
end
end
My questions are how do I do search irrespective of pluralization?
tshirt, T-shirt, Tshirts should all match.
Above all I never found any explanation of the following block given below
settings index: { number_of_shards: 1 } do
mappings dynamic: 'false' do
indexes :name, analyzer: 'snowball', index_options: 'offsets'
indexes :description, analyzer: 'snowball'
indexes :category, analyzer: 'snowball'
end
end
what is the exact purpose of this block for searching.
what does mappings dynamic: 'false' means?
what does indexes :name, analyzer: 'snowball', index_options: 'offsets'
means?
What are the other options that could be added in this block with a little bit of explanation would be of great help for me.
Any links for further research is also helpful.
Thanks